Javascript alert on incomplete variables












2















i'm having troubles on javascript arithmetic.
lets say i have 2 elements from html,



var num1 = document.getElementByID('one').value;

var num2 = docuemnt.getElementByID('two').value;



var total = num1 + num2;



alert(total);


these two elements are inputted by users. lets say the user left the id='one' blank. how do i make javascript still compute and alert 'total'? can javascript automatically set the blank field to '0'? i tried this on my project but it will only give me an alert if both 'one' and 'two' were given/inputted. maybe i'm missing something.



Thanks for any help.



ok this is the code i'm using on my project,



var number = document.getElementById('child1').value;

var hrs = document.getElementById('hrs1').value;

var qty = document.getElementById('qty1').value;

var watts = qty * (number / 1000);

var kwh = watts * hrs;

var kwhh = kwh * 30;



var number2 = document.getElementById('child2').value;

var hrs2 = document.getElementById('hrs2').value;

var qty2 = document.getElementById('qty2').value;

var watts2 = qty2 * (number2 / 1000);

var kwh2 = watts2 * hrs2;

var kwhh2 = kwh2 * 30;



var totalperhr = kwh+kwh2;

var totalper30 = kwhh+kwhh2;



alert(totalperhr + ' kwh per dayn' + totalper30 + ' kwh per 30 days');


html below,



<input type="range" min="1" max="1000" id="child1">

<select id="hrs1">

    <option value='1'>1hr</option>

    <option value='2'>2hr</option>

    <option value='3'>3hr</option>

</select>

<select id="qty1">

    <option value='1'>1</option>

    <option value='2'>2</option>

    <option value='2'>3</option>

</select>



<input type="range" min="1" max="1000" id="child2">

<select id="hrs2">

    <option value='1'>1hr</option>

    <option value='2'>2hr</option>

    <option value='3'>3hr</option>

</select>

<select id="qty2">

    <option value='1'>1</option>

    <option value='2'>2</option>

    <option value='2'>3</option>

</select>


as you can see, i'm going thru several operations then getting the grand total. but i'm not getting any alerts if i leave one blank.






javascript html







share|improve this question




















  • 2





    Sounds odd, it shouldn't throw an error - if the value is empty, it will default to the empty string, which is perfectly concatenatable

    – CertainPerformance
    Nov 14 '18 at 6:15













  • FYI, <input> value properties are always strings, even <input type="number">

    – Phil
    Nov 14 '18 at 6:19
















2















i'm having troubles on javascript arithmetic.
lets say i have 2 elements from html,



var num1 = document.getElementByID('one').value;

var num2 = docuemnt.getElementByID('two').value;



var total = num1 + num2;



alert(total);


these two elements are inputted by users. lets say the user left the id='one' blank. how do i make javascript still compute and alert 'total'? can javascript automatically set the blank field to '0'? i tried this on my project but it will only give me an alert if both 'one' and 'two' were given/inputted. maybe i'm missing something.



Thanks for any help.



ok this is the code i'm using on my project,



var number = document.getElementById('child1').value;

var hrs = document.getElementById('hrs1').value;

var qty = document.getElementById('qty1').value;

var watts = qty * (number / 1000);

var kwh = watts * hrs;

var kwhh = kwh * 30;



var number2 = document.getElementById('child2').value;

var hrs2 = document.getElementById('hrs2').value;

var qty2 = document.getElementById('qty2').value;

var watts2 = qty2 * (number2 / 1000);

var kwh2 = watts2 * hrs2;

var kwhh2 = kwh2 * 30;



var totalperhr = kwh+kwh2;

var totalper30 = kwhh+kwhh2;



alert(totalperhr + ' kwh per dayn' + totalper30 + ' kwh per 30 days');


html below,



<input type="range" min="1" max="1000" id="child1">

<select id="hrs1">

    <option value='1'>1hr</option>

    <option value='2'>2hr</option>

    <option value='3'>3hr</option>

</select>

<select id="qty1">

    <option value='1'>1</option>

    <option value='2'>2</option>

    <option value='2'>3</option>

</select>



<input type="range" min="1" max="1000" id="child2">

<select id="hrs2">

    <option value='1'>1hr</option>

    <option value='2'>2hr</option>

    <option value='3'>3hr</option>

</select>

<select id="qty2">

    <option value='1'>1</option>

    <option value='2'>2</option>

    <option value='2'>3</option>

</select>


as you can see, i'm going thru several operations then getting the grand total. but i'm not getting any alerts if i leave one blank.






javascript html







share|improve this question




















  • 2





    Sounds odd, it shouldn't throw an error - if the value is empty, it will default to the empty string, which is perfectly concatenatable

    – CertainPerformance
    Nov 14 '18 at 6:15













  • FYI, <input> value properties are always strings, even <input type="number">

    – Phil
    Nov 14 '18 at 6:19














2












2








2


1






i'm having troubles on javascript arithmetic.
lets say i have 2 elements from html,



var num1 = document.getElementByID('one').value;

var num2 = docuemnt.getElementByID('two').value;



var total = num1 + num2;



alert(total);


these two elements are inputted by users. lets say the user left the id='one' blank. how do i make javascript still compute and alert 'total'? can javascript automatically set the blank field to '0'? i tried this on my project but it will only give me an alert if both 'one' and 'two' were given/inputted. maybe i'm missing something.



Thanks for any help.



ok this is the code i'm using on my project,



var number = document.getElementById('child1').value;

var hrs = document.getElementById('hrs1').value;

var qty = document.getElementById('qty1').value;

var watts = qty * (number / 1000);

var kwh = watts * hrs;

var kwhh = kwh * 30;



var number2 = document.getElementById('child2').value;

var hrs2 = document.getElementById('hrs2').value;

var qty2 = document.getElementById('qty2').value;

var watts2 = qty2 * (number2 / 1000);

var kwh2 = watts2 * hrs2;

var kwhh2 = kwh2 * 30;



var totalperhr = kwh+kwh2;

var totalper30 = kwhh+kwhh2;



alert(totalperhr + ' kwh per dayn' + totalper30 + ' kwh per 30 days');


html below,



<input type="range" min="1" max="1000" id="child1">

<select id="hrs1">

    <option value='1'>1hr</option>

    <option value='2'>2hr</option>

    <option value='3'>3hr</option>

</select>

<select id="qty1">

    <option value='1'>1</option>

    <option value='2'>2</option>

    <option value='2'>3</option>

</select>



<input type="range" min="1" max="1000" id="child2">

<select id="hrs2">

    <option value='1'>1hr</option>

    <option value='2'>2hr</option>

    <option value='3'>3hr</option>

</select>

<select id="qty2">

    <option value='1'>1</option>

    <option value='2'>2</option>

    <option value='2'>3</option>

</select>


as you can see, i'm going thru several operations then getting the grand total. but i'm not getting any alerts if i leave one blank.






javascript html







share|improve this question
















i'm having troubles on javascript arithmetic.
lets say i have 2 elements from html,



var num1 = document.getElementByID('one').value;

var num2 = docuemnt.getElementByID('two').value;



var total = num1 + num2;



alert(total);


these two elements are inputted by users. lets say the user left the id='one' blank. how do i make javascript still compute and alert 'total'? can javascript automatically set the blank field to '0'? i tried this on my project but it will only give me an alert if both 'one' and 'two' were given/inputted. maybe i'm missing something.



Thanks for any help.



ok this is the code i'm using on my project,



var number = document.getElementById('child1').value;

var hrs = document.getElementById('hrs1').value;

var qty = document.getElementById('qty1').value;

var watts = qty * (number / 1000);

var kwh = watts * hrs;

var kwhh = kwh * 30;



var number2 = document.getElementById('child2').value;

var hrs2 = document.getElementById('hrs2').value;

var qty2 = document.getElementById('qty2').value;

var watts2 = qty2 * (number2 / 1000);

var kwh2 = watts2 * hrs2;

var kwhh2 = kwh2 * 30;



var totalperhr = kwh+kwh2;

var totalper30 = kwhh+kwhh2;



alert(totalperhr + ' kwh per dayn' + totalper30 + ' kwh per 30 days');


html below,



<input type="range" min="1" max="1000" id="child1">

<select id="hrs1">

    <option value='1'>1hr</option>

    <option value='2'>2hr</option>

    <option value='3'>3hr</option>

</select>

<select id="qty1">

    <option value='1'>1</option>

    <option value='2'>2</option>

    <option value='2'>3</option>

</select>



<input type="range" min="1" max="1000" id="child2">

<select id="hrs2">

    <option value='1'>1hr</option>

    <option value='2'>2hr</option>

    <option value='3'>3hr</option>

</select>

<select id="qty2">

    <option value='1'>1</option>

    <option value='2'>2</option>

    <option value='2'>3</option>

</select>


as you can see, i'm going thru several operations then getting the grand total. but i'm not getting any alerts if i leave one blank.






javascript html




javascript html






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Nov 14 '18 at 6:48







Kim Lo

















asked Nov 14 '18 at 6:14









Kim LoKim Lo

295




295








  • 2





    Sounds odd, it shouldn't throw an error - if the value is empty, it will default to the empty string, which is perfectly concatenatable

    – CertainPerformance
    Nov 14 '18 at 6:15













  • FYI, <input> value properties are always strings, even <input type="number">

    – Phil
    Nov 14 '18 at 6:19














  • 2





    Sounds odd, it shouldn't throw an error - if the value is empty, it will default to the empty string, which is perfectly concatenatable

    – CertainPerformance
    Nov 14 '18 at 6:15













  • FYI, <input> value properties are always strings, even <input type="number">

    – Phil
    Nov 14 '18 at 6:19








2




2





Sounds odd, it shouldn't throw an error - if the value is empty, it will default to the empty string, which is perfectly concatenatable

– CertainPerformance
Nov 14 '18 at 6:15







Sounds odd, it shouldn't throw an error - if the value is empty, it will default to the empty string, which is perfectly concatenatable

– CertainPerformance
Nov 14 '18 at 6:15















FYI, <input> value properties are always strings, even <input type="number">

– Phil
Nov 14 '18 at 6:19





FYI, <input> value properties are always strings, even <input type="number">

– Phil
Nov 14 '18 at 6:19












1 Answer
1






active

oldest

votes


















8














You can use Unary plus (+) operator to get the number out of the value property of your input, or set it to 0:



+document.getElementById('one').value || 0;


Code example:






const num1 = +document.getElementById('one').value || 0;

const num2 = +document.getElementById('two').value || 0;



const total = num1 + num2;



console.log(total);

<input type="number" value="5" name="one" id="one">

<input type="number" value="" name="two" id="two">





Note: instead of document.getElementByID() you should write document.getElementById()



Your code:






const elements = document.querySelectorAll('#child1, #hrs1, #qty1, #child2, #hrs2, #qty2');

const values = {

  child1: 0,

  hrs1: 0,

  qty1: 0,

  child2: 0,

  hrs2: 0,

  qty2: 0

};

const getTotals = () => {

  elements.forEach(elem => values[elem.id] = +elem.value || 0);



  const watts = values.qty1 * (values.child1 / 1000);

  const kwh = watts * values.hrs1;

  const kwhh = kwh * 30;



  const watts2 = values.qty2 * (values.child2 / 1000);

  const kwh2 = watts2 * values.hrs2;

  const kwhh2 = kwh2 * 30;



  const totalperhr = kwh + kwh2;

  const totalper30 = kwhh + kwhh2;



  console.clear();

  console.log(values);

  console.log(totalperhr + ' kwh per dayn' + totalper30 + ' kwh per 30 days');

};



elements.forEach(elem => elem.addEventListener('change', getTotals));

<input type="range" min="1" max="1000" id="child1">

<select id="hrs1">

  <option value=""></option>

  <option value="1">1hr</option>

  <option value="2">2hr</option>

  <option value="3">3hr</option>

</select>

<select id="qty1">

  <option value=""></option>

  <option value="1">1</option>

  <option value="2">2</option>

  <option value="2">3</option>

</select>



<input type="range" min="1" max="1000" id="child2">

<select id="hrs2">

  <option value=""></option>

  <option value="1">1hr</option>

  <option value="2">2hr</option>

  <option value="3">3hr</option>

</select>

<select id="qty2">

  <option value=""></option>

  <option value="1">1</option>

  <option value="2">2</option>

  <option value="2">3</option>

</select>








share|improve this answer


























  • hi sir, i edited my question above with my actual code i'm using. i tried this but can't get it to work.

    – Kim Lo
    Nov 14 '18 at 6:38











  • Can you also add the html code please?

    – Yosvel Quintero
    Nov 14 '18 at 6:39











  • -1, the answer is misleading. As @CertainPerformance has pointed out "if the value is empty, it will default to the empty string, which is perfectly concatenatable". I. e., console.log(42 + ''); returns 42. This snippet will also work after removing the unary operator and the || 0.

    – David
    Nov 14 '18 at 6:44








  • 1





    @David that is a not good comment. I will never recommend to anybody that uses a string in a matematic operation.. Because if there is a number what will happen?: console.log(42 + '0'); return 420

    – Yosvel Quintero
    Nov 14 '18 at 6:48






  • 1





    @YosvelQuintero - That's completely correct. I didn't say that your answer is wrong. I said that is misleading because clearly that's not the OP problem. At least, not the only one.

    – David
    Nov 14 '18 at 6:49













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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









8














You can use Unary plus (+) operator to get the number out of the value property of your input, or set it to 0:



+document.getElementById('one').value || 0;


Code example:






const num1 = +document.getElementById('one').value || 0;

const num2 = +document.getElementById('two').value || 0;



const total = num1 + num2;



console.log(total);

<input type="number" value="5" name="one" id="one">

<input type="number" value="" name="two" id="two">





Note: instead of document.getElementByID() you should write document.getElementById()



Your code:






const elements = document.querySelectorAll('#child1, #hrs1, #qty1, #child2, #hrs2, #qty2');

const values = {

  child1: 0,

  hrs1: 0,

  qty1: 0,

  child2: 0,

  hrs2: 0,

  qty2: 0

};

const getTotals = () => {

  elements.forEach(elem => values[elem.id] = +elem.value || 0);



  const watts = values.qty1 * (values.child1 / 1000);

  const kwh = watts * values.hrs1;

  const kwhh = kwh * 30;



  const watts2 = values.qty2 * (values.child2 / 1000);

  const kwh2 = watts2 * values.hrs2;

  const kwhh2 = kwh2 * 30;



  const totalperhr = kwh + kwh2;

  const totalper30 = kwhh + kwhh2;



  console.clear();

  console.log(values);

  console.log(totalperhr + ' kwh per dayn' + totalper30 + ' kwh per 30 days');

};



elements.forEach(elem => elem.addEventListener('change', getTotals));

<input type="range" min="1" max="1000" id="child1">

<select id="hrs1">

  <option value=""></option>

  <option value="1">1hr</option>

  <option value="2">2hr</option>

  <option value="3">3hr</option>

</select>

<select id="qty1">

  <option value=""></option>

  <option value="1">1</option>

  <option value="2">2</option>

  <option value="2">3</option>

</select>



<input type="range" min="1" max="1000" id="child2">

<select id="hrs2">

  <option value=""></option>

  <option value="1">1hr</option>

  <option value="2">2hr</option>

  <option value="3">3hr</option>

</select>

<select id="qty2">

  <option value=""></option>

  <option value="1">1</option>

  <option value="2">2</option>

  <option value="2">3</option>

</select>








share|improve this answer


























  • hi sir, i edited my question above with my actual code i'm using. i tried this but can't get it to work.

    – Kim Lo
    Nov 14 '18 at 6:38











  • Can you also add the html code please?

    – Yosvel Quintero
    Nov 14 '18 at 6:39











  • -1, the answer is misleading. As @CertainPerformance has pointed out "if the value is empty, it will default to the empty string, which is perfectly concatenatable". I. e., console.log(42 + ''); returns 42. This snippet will also work after removing the unary operator and the || 0.

    – David
    Nov 14 '18 at 6:44








  • 1





    @David that is a not good comment. I will never recommend to anybody that uses a string in a matematic operation.. Because if there is a number what will happen?: console.log(42 + '0'); return 420

    – Yosvel Quintero
    Nov 14 '18 at 6:48






  • 1





    @YosvelQuintero - That's completely correct. I didn't say that your answer is wrong. I said that is misleading because clearly that's not the OP problem. At least, not the only one.

    – David
    Nov 14 '18 at 6:49


















8














You can use Unary plus (+) operator to get the number out of the value property of your input, or set it to 0:



+document.getElementById('one').value || 0;


Code example:






const num1 = +document.getElementById('one').value || 0;

const num2 = +document.getElementById('two').value || 0;



const total = num1 + num2;



console.log(total);

<input type="number" value="5" name="one" id="one">

<input type="number" value="" name="two" id="two">





Note: instead of document.getElementByID() you should write document.getElementById()



Your code:






const elements = document.querySelectorAll('#child1, #hrs1, #qty1, #child2, #hrs2, #qty2');

const values = {

  child1: 0,

  hrs1: 0,

  qty1: 0,

  child2: 0,

  hrs2: 0,

  qty2: 0

};

const getTotals = () => {

  elements.forEach(elem => values[elem.id] = +elem.value || 0);



  const watts = values.qty1 * (values.child1 / 1000);

  const kwh = watts * values.hrs1;

  const kwhh = kwh * 30;



  const watts2 = values.qty2 * (values.child2 / 1000);

  const kwh2 = watts2 * values.hrs2;

  const kwhh2 = kwh2 * 30;



  const totalperhr = kwh + kwh2;

  const totalper30 = kwhh + kwhh2;



  console.clear();

  console.log(values);

  console.log(totalperhr + ' kwh per dayn' + totalper30 + ' kwh per 30 days');

};



elements.forEach(elem => elem.addEventListener('change', getTotals));

<input type="range" min="1" max="1000" id="child1">

<select id="hrs1">

  <option value=""></option>

  <option value="1">1hr</option>

  <option value="2">2hr</option>

  <option value="3">3hr</option>

</select>

<select id="qty1">

  <option value=""></option>

  <option value="1">1</option>

  <option value="2">2</option>

  <option value="2">3</option>

</select>



<input type="range" min="1" max="1000" id="child2">

<select id="hrs2">

  <option value=""></option>

  <option value="1">1hr</option>

  <option value="2">2hr</option>

  <option value="3">3hr</option>

</select>

<select id="qty2">

  <option value=""></option>

  <option value="1">1</option>

  <option value="2">2</option>

  <option value="2">3</option>

</select>








share|improve this answer


























  • hi sir, i edited my question above with my actual code i'm using. i tried this but can't get it to work.

    – Kim Lo
    Nov 14 '18 at 6:38











  • Can you also add the html code please?

    – Yosvel Quintero
    Nov 14 '18 at 6:39











  • -1, the answer is misleading. As @CertainPerformance has pointed out "if the value is empty, it will default to the empty string, which is perfectly concatenatable". I. e., console.log(42 + ''); returns 42. This snippet will also work after removing the unary operator and the || 0.

    – David
    Nov 14 '18 at 6:44








  • 1





    @David that is a not good comment. I will never recommend to anybody that uses a string in a matematic operation.. Because if there is a number what will happen?: console.log(42 + '0'); return 420

    – Yosvel Quintero
    Nov 14 '18 at 6:48






  • 1





    @YosvelQuintero - That's completely correct. I didn't say that your answer is wrong. I said that is misleading because clearly that's not the OP problem. At least, not the only one.

    – David
    Nov 14 '18 at 6:49
















8












8








8







You can use Unary plus (+) operator to get the number out of the value property of your input, or set it to 0:



+document.getElementById('one').value || 0;


Code example:






const num1 = +document.getElementById('one').value || 0;

const num2 = +document.getElementById('two').value || 0;



const total = num1 + num2;



console.log(total);

<input type="number" value="5" name="one" id="one">

<input type="number" value="" name="two" id="two">





Note: instead of document.getElementByID() you should write document.getElementById()



Your code:






const elements = document.querySelectorAll('#child1, #hrs1, #qty1, #child2, #hrs2, #qty2');

const values = {

  child1: 0,

  hrs1: 0,

  qty1: 0,

  child2: 0,

  hrs2: 0,

  qty2: 0

};

const getTotals = () => {

  elements.forEach(elem => values[elem.id] = +elem.value || 0);



  const watts = values.qty1 * (values.child1 / 1000);

  const kwh = watts * values.hrs1;

  const kwhh = kwh * 30;



  const watts2 = values.qty2 * (values.child2 / 1000);

  const kwh2 = watts2 * values.hrs2;

  const kwhh2 = kwh2 * 30;



  const totalperhr = kwh + kwh2;

  const totalper30 = kwhh + kwhh2;



  console.clear();

  console.log(values);

  console.log(totalperhr + ' kwh per dayn' + totalper30 + ' kwh per 30 days');

};



elements.forEach(elem => elem.addEventListener('change', getTotals));

<input type="range" min="1" max="1000" id="child1">

<select id="hrs1">

  <option value=""></option>

  <option value="1">1hr</option>

  <option value="2">2hr</option>

  <option value="3">3hr</option>

</select>

<select id="qty1">

  <option value=""></option>

  <option value="1">1</option>

  <option value="2">2</option>

  <option value="2">3</option>

</select>



<input type="range" min="1" max="1000" id="child2">

<select id="hrs2">

  <option value=""></option>

  <option value="1">1hr</option>

  <option value="2">2hr</option>

  <option value="3">3hr</option>

</select>

<select id="qty2">

  <option value=""></option>

  <option value="1">1</option>

  <option value="2">2</option>

  <option value="2">3</option>

</select>








share|improve this answer















You can use Unary plus (+) operator to get the number out of the value property of your input, or set it to 0:



+document.getElementById('one').value || 0;


Code example:






const num1 = +document.getElementById('one').value || 0;

const num2 = +document.getElementById('two').value || 0;



const total = num1 + num2;



console.log(total);

<input type="number" value="5" name="one" id="one">

<input type="number" value="" name="two" id="two">





Note: instead of document.getElementByID() you should write document.getElementById()



Your code:






const elements = document.querySelectorAll('#child1, #hrs1, #qty1, #child2, #hrs2, #qty2');

const values = {

  child1: 0,

  hrs1: 0,

  qty1: 0,

  child2: 0,

  hrs2: 0,

  qty2: 0

};

const getTotals = () => {

  elements.forEach(elem => values[elem.id] = +elem.value || 0);



  const watts = values.qty1 * (values.child1 / 1000);

  const kwh = watts * values.hrs1;

  const kwhh = kwh * 30;



  const watts2 = values.qty2 * (values.child2 / 1000);

  const kwh2 = watts2 * values.hrs2;

  const kwhh2 = kwh2 * 30;



  const totalperhr = kwh + kwh2;

  const totalper30 = kwhh + kwhh2;



  console.clear();

  console.log(values);

  console.log(totalperhr + ' kwh per dayn' + totalper30 + ' kwh per 30 days');

};



elements.forEach(elem => elem.addEventListener('change', getTotals));

<input type="range" min="1" max="1000" id="child1">

<select id="hrs1">

  <option value=""></option>

  <option value="1">1hr</option>

  <option value="2">2hr</option>

  <option value="3">3hr</option>

</select>

<select id="qty1">

  <option value=""></option>

  <option value="1">1</option>

  <option value="2">2</option>

  <option value="2">3</option>

</select>



<input type="range" min="1" max="1000" id="child2">

<select id="hrs2">

  <option value=""></option>

  <option value="1">1hr</option>

  <option value="2">2hr</option>

  <option value="3">3hr</option>

</select>

<select id="qty2">

  <option value=""></option>

  <option value="1">1</option>

  <option value="2">2</option>

  <option value="2">3</option>

</select>








const num1 = +document.getElementById('one').value || 0;

const num2 = +document.getElementById('two').value || 0;



const total = num1 + num2;



console.log(total);

<input type="number" value="5" name="one" id="one">

<input type="number" value="" name="two" id="two">





const num1 = +document.getElementById('one').value || 0;

const num2 = +document.getElementById('two').value || 0;



const total = num1 + num2;



console.log(total);

<input type="number" value="5" name="one" id="one">

<input type="number" value="" name="two" id="two">





const elements = document.querySelectorAll('#child1, #hrs1, #qty1, #child2, #hrs2, #qty2');

const values = {

  child1: 0,

  hrs1: 0,

  qty1: 0,

  child2: 0,

  hrs2: 0,

  qty2: 0

};

const getTotals = () => {

  elements.forEach(elem => values[elem.id] = +elem.value || 0);



  const watts = values.qty1 * (values.child1 / 1000);

  const kwh = watts * values.hrs1;

  const kwhh = kwh * 30;



  const watts2 = values.qty2 * (values.child2 / 1000);

  const kwh2 = watts2 * values.hrs2;

  const kwhh2 = kwh2 * 30;



  const totalperhr = kwh + kwh2;

  const totalper30 = kwhh + kwhh2;



  console.clear();

  console.log(values);

  console.log(totalperhr + ' kwh per dayn' + totalper30 + ' kwh per 30 days');

};



elements.forEach(elem => elem.addEventListener('change', getTotals));

<input type="range" min="1" max="1000" id="child1">

<select id="hrs1">

  <option value=""></option>

  <option value="1">1hr</option>

  <option value="2">2hr</option>

  <option value="3">3hr</option>

</select>

<select id="qty1">

  <option value=""></option>

  <option value="1">1</option>

  <option value="2">2</option>

  <option value="2">3</option>

</select>



<input type="range" min="1" max="1000" id="child2">

<select id="hrs2">

  <option value=""></option>

  <option value="1">1hr</option>

  <option value="2">2hr</option>

  <option value="3">3hr</option>

</select>

<select id="qty2">

  <option value=""></option>

  <option value="1">1</option>

  <option value="2">2</option>

  <option value="2">3</option>

</select>





const elements = document.querySelectorAll('#child1, #hrs1, #qty1, #child2, #hrs2, #qty2');

const values = {

  child1: 0,

  hrs1: 0,

  qty1: 0,

  child2: 0,

  hrs2: 0,

  qty2: 0

};

const getTotals = () => {

  elements.forEach(elem => values[elem.id] = +elem.value || 0);



  const watts = values.qty1 * (values.child1 / 1000);

  const kwh = watts * values.hrs1;

  const kwhh = kwh * 30;



  const watts2 = values.qty2 * (values.child2 / 1000);

  const kwh2 = watts2 * values.hrs2;

  const kwhh2 = kwh2 * 30;



  const totalperhr = kwh + kwh2;

  const totalper30 = kwhh + kwhh2;



  console.clear();

  console.log(values);

  console.log(totalperhr + ' kwh per dayn' + totalper30 + ' kwh per 30 days');

};



elements.forEach(elem => elem.addEventListener('change', getTotals));

<input type="range" min="1" max="1000" id="child1">

<select id="hrs1">

  <option value=""></option>

  <option value="1">1hr</option>

  <option value="2">2hr</option>

  <option value="3">3hr</option>

</select>

<select id="qty1">

  <option value=""></option>

  <option value="1">1</option>

  <option value="2">2</option>

  <option value="2">3</option>

</select>



<input type="range" min="1" max="1000" id="child2">

<select id="hrs2">

  <option value=""></option>

  <option value="1">1hr</option>

  <option value="2">2hr</option>

  <option value="3">3hr</option>

</select>

<select id="qty2">

  <option value=""></option>

  <option value="1">1</option>

  <option value="2">2</option>

  <option value="2">3</option>

</select>






share|improve this answer














share|improve this answer



share|improve this answer








edited Nov 14 '18 at 7:45

























answered Nov 14 '18 at 6:17









Yosvel QuinteroYosvel Quintero

11k42429




11k42429













  • hi sir, i edited my question above with my actual code i'm using. i tried this but can't get it to work.

    – Kim Lo
    Nov 14 '18 at 6:38











  • Can you also add the html code please?

    – Yosvel Quintero
    Nov 14 '18 at 6:39











  • -1, the answer is misleading. As @CertainPerformance has pointed out "if the value is empty, it will default to the empty string, which is perfectly concatenatable". I. e., console.log(42 + ''); returns 42. This snippet will also work after removing the unary operator and the || 0.

    – David
    Nov 14 '18 at 6:44








  • 1





    @David that is a not good comment. I will never recommend to anybody that uses a string in a matematic operation.. Because if there is a number what will happen?: console.log(42 + '0'); return 420

    – Yosvel Quintero
    Nov 14 '18 at 6:48






  • 1





    @YosvelQuintero - That's completely correct. I didn't say that your answer is wrong. I said that is misleading because clearly that's not the OP problem. At least, not the only one.

    – David
    Nov 14 '18 at 6:49





















  • hi sir, i edited my question above with my actual code i'm using. i tried this but can't get it to work.

    – Kim Lo
    Nov 14 '18 at 6:38











  • Can you also add the html code please?

    – Yosvel Quintero
    Nov 14 '18 at 6:39











  • -1, the answer is misleading. As @CertainPerformance has pointed out "if the value is empty, it will default to the empty string, which is perfectly concatenatable". I. e., console.log(42 + ''); returns 42. This snippet will also work after removing the unary operator and the || 0.

    – David
    Nov 14 '18 at 6:44








  • 1





    @David that is a not good comment. I will never recommend to anybody that uses a string in a matematic operation.. Because if there is a number what will happen?: console.log(42 + '0'); return 420

    – Yosvel Quintero
    Nov 14 '18 at 6:48






  • 1





    @YosvelQuintero - That's completely correct. I didn't say that your answer is wrong. I said that is misleading because clearly that's not the OP problem. At least, not the only one.

    – David
    Nov 14 '18 at 6:49



















hi sir, i edited my question above with my actual code i'm using. i tried this but can't get it to work.

– Kim Lo
Nov 14 '18 at 6:38





hi sir, i edited my question above with my actual code i'm using. i tried this but can't get it to work.

– Kim Lo
Nov 14 '18 at 6:38













Can you also add the html code please?

– Yosvel Quintero
Nov 14 '18 at 6:39





Can you also add the html code please?

– Yosvel Quintero
Nov 14 '18 at 6:39













-1, the answer is misleading. As @CertainPerformance has pointed out "if the value is empty, it will default to the empty string, which is perfectly concatenatable". I. e., console.log(42 + ''); returns 42. This snippet will also work after removing the unary operator and the || 0.

– David
Nov 14 '18 at 6:44







-1, the answer is misleading. As @CertainPerformance has pointed out "if the value is empty, it will default to the empty string, which is perfectly concatenatable". I. e., console.log(42 + ''); returns 42. This snippet will also work after removing the unary operator and the || 0.

– David
Nov 14 '18 at 6:44






1




1





@David that is a not good comment. I will never recommend to anybody that uses a string in a matematic operation.. Because if there is a number what will happen?: console.log(42 + '0'); return 420

– Yosvel Quintero
Nov 14 '18 at 6:48





@David that is a not good comment. I will never recommend to anybody that uses a string in a matematic operation.. Because if there is a number what will happen?: console.log(42 + '0'); return 420

– Yosvel Quintero
Nov 14 '18 at 6:48




1




1





@YosvelQuintero - That's completely correct. I didn't say that your answer is wrong. I said that is misleading because clearly that's not the OP problem. At least, not the only one.

– David
Nov 14 '18 at 6:49







@YosvelQuintero - That's completely correct. I didn't say that your answer is wrong. I said that is misleading because clearly that's not the OP problem. At least, not the only one.

– David
Nov 14 '18 at 6:49




















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