Delete all elements in an array - Function appends 'undefined' at the array end

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-1

Here is my code

var x = ;



function random(min,max) {

  return Math.floor(Math.random() * (min-max))+min;

}

function random2(a, b) {

  for (let i = 0; i < a; i++) {

    x.push(random(0,b));

  }

}

random2(5, 100);

console.log(x); // [ -43, -27, -38, -21, -79 ]



x.splice(0, x.length);

x.push(random2(5,100));

console.log(x); // [ -24, -97, -99, -43, -66, undefined ]

I simply wanna remove all the elements in the array then add new elements in it.
But when I try to do it with the code above, undefined is also adding to the array.
How can I prevent it?

edited Nov 16 '18 at 13:36

Vignesh Raja

3,02211121

asked Nov 16 '18 at 13:15

uhbc

526

4

why not just reset it with x = ?

– chazsolo
Nov 16 '18 at 13:16

3

so, what about x = ; instead of splicing and whatever?

– briosheje
Nov 16 '18 at 13:16

3

or x.length = 0;

– Nina Scholz
Nov 16 '18 at 13:17

1

Why don't you just assign empty array to it? 'x='

– Slobodan Gajić
Nov 16 '18 at 13:17

2

Possible duplicate of How do I empty an array in JavaScript?

– kemicofa
Nov 16 '18 at 13:21

|
show 2 more comments

-1

Here is my code

var x = ;



function random(min,max) {

  return Math.floor(Math.random() * (min-max))+min;

}

function random2(a, b) {

  for (let i = 0; i < a; i++) {

    x.push(random(0,b));

  }

}

random2(5, 100);

console.log(x); // [ -43, -27, -38, -21, -79 ]



x.splice(0, x.length);

x.push(random2(5,100));

console.log(x); // [ -24, -97, -99, -43, -66, undefined ]

I simply wanna remove all the elements in the array then add new elements in it.
But when I try to do it with the code above, undefined is also adding to the array.
How can I prevent it?

edited Nov 16 '18 at 13:36

Vignesh Raja

3,02211121

asked Nov 16 '18 at 13:15

uhbc

526

4

why not just reset it with x = ?

– chazsolo
Nov 16 '18 at 13:16

3

so, what about x = ; instead of splicing and whatever?

– briosheje
Nov 16 '18 at 13:16

3

or x.length = 0;

– Nina Scholz
Nov 16 '18 at 13:17

1

Why don't you just assign empty array to it? 'x='

– Slobodan Gajić
Nov 16 '18 at 13:17

2

Possible duplicate of How do I empty an array in JavaScript?

– kemicofa
Nov 16 '18 at 13:21

|
show 2 more comments

-1

Here is my code

var x = ;



function random(min,max) {

  return Math.floor(Math.random() * (min-max))+min;

}

function random2(a, b) {

  for (let i = 0; i < a; i++) {

    x.push(random(0,b));

  }

}

random2(5, 100);

console.log(x); // [ -43, -27, -38, -21, -79 ]



x.splice(0, x.length);

x.push(random2(5,100));

console.log(x); // [ -24, -97, -99, -43, -66, undefined ]

I simply wanna remove all the elements in the array then add new elements in it.
But when I try to do it with the code above, undefined is also adding to the array.
How can I prevent it?

edited Nov 16 '18 at 13:36

Vignesh Raja

3,02211121

asked Nov 16 '18 at 13:15

uhbc

526

Here is my code

var x = ;



function random(min,max) {

  return Math.floor(Math.random() * (min-max))+min;

}

function random2(a, b) {

  for (let i = 0; i < a; i++) {

    x.push(random(0,b));

  }

}

random2(5, 100);

console.log(x); // [ -43, -27, -38, -21, -79 ]



x.splice(0, x.length);

x.push(random2(5,100));

console.log(x); // [ -24, -97, -99, -43, -66, undefined ]

I simply wanna remove all the elements in the array then add new elements in it.
But when I try to do it with the code above, undefined is also adding to the array.
How can I prevent it?

javascript arrays push splice

edited Nov 16 '18 at 13:36

Vignesh Raja

3,02211121

asked Nov 16 '18 at 13:15

uhbc

526

edited Nov 16 '18 at 13:36

Vignesh Raja

3,02211121

asked Nov 16 '18 at 13:15

uhbc

526

edited Nov 16 '18 at 13:36

Vignesh Raja

3,02211121

edited Nov 16 '18 at 13:36

Vignesh Raja

3,02211121

edited Nov 16 '18 at 13:36

Vignesh Raja

3,02211121

asked Nov 16 '18 at 13:15

uhbc

526

asked Nov 16 '18 at 13:15

uhbc

526

asked Nov 16 '18 at 13:15

uhbc

526

4

why not just reset it with x = ?

– chazsolo
Nov 16 '18 at 13:16

3

so, what about x = ; instead of splicing and whatever?

– briosheje
Nov 16 '18 at 13:16

3

or x.length = 0;

– Nina Scholz
Nov 16 '18 at 13:17

1

Why don't you just assign empty array to it? 'x='

– Slobodan Gajić
Nov 16 '18 at 13:17

2

Possible duplicate of How do I empty an array in JavaScript?

– kemicofa
Nov 16 '18 at 13:21

|
show 2 more comments

4

why not just reset it with x = ?

– chazsolo
Nov 16 '18 at 13:16

3

so, what about x = ; instead of splicing and whatever?

– briosheje
Nov 16 '18 at 13:16

3

or x.length = 0;

– Nina Scholz
Nov 16 '18 at 13:17

1

Why don't you just assign empty array to it? 'x='

– Slobodan Gajić
Nov 16 '18 at 13:17

2

Possible duplicate of How do I empty an array in JavaScript?

– kemicofa
Nov 16 '18 at 13:21

why not just reset it with x = ?

– chazsolo
Nov 16 '18 at 13:16

so, what about x = ; instead of splicing and whatever?

– briosheje
Nov 16 '18 at 13:16

or x.length = 0;

– Nina Scholz
Nov 16 '18 at 13:17

Why don't you just assign empty array to it? 'x='

– Slobodan Gajić
Nov 16 '18 at 13:17

Possible duplicate of How do I empty an array in JavaScript?

– kemicofa
Nov 16 '18 at 13:21

|
show 2 more comments

3 Answers
3

active

oldest

votes

You need not to puish the function call, which returns undefined, but just call the function random2, because the function itselft add the elements to the array.

function random(min, max) {

    return Math.floor(Math.random() * (min - max)) + min;

}



function random2(a, b) {

    for (let i = 0; i < a; i++) {

        x.push(random(0, b));

    }

}



var x = ;



random2(5, 100);

console.log(x);



x.length = 0;          // better performance than x.splice(0, x.length)

random2(5,100);        // call without using push

console.log(x);        // no undefined anymore

A better approach is to return an array in random2, because this function does not access an outer defined array. To push the values, you could take the spread syntax.

function random(min, max) {

    return Math.floor(Math.random() * (min - max)) + min;

}



function random2(a, b) {

    return Array.from({ length: a }, _ => random(0, b));

}



var x = random2(5, 100);

console.log(x);



x.length = 0;          

x.push(...random2(5, 100));

console.log(x);

edited Nov 16 '18 at 13:30

answered Nov 16 '18 at 13:22

Nina Scholz

196k15109179

After 3h of sleep haven't thought of it, thanks

– uhbc
Nov 16 '18 at 13:26

@nina, Out of the context, isn't it should be random(a,b) inside random2 method, assuming the OP need to create min number of random numbers between min and max values ? Even the OP is wrong in his implementation.

– Vignesh Raja
Nov 16 '18 at 13:40

@VigneshRaja, please ask op.

– Nina Scholz
Nov 16 '18 at 13:42

add a comment |

To empty an array, there are multiple ways as explained here with some benchmark results and explanation regarding their performance.

As an aggregation, asssume var a = [1,2,3,4,5]

a =

a.length = 0

a.splice(0, a.length)

a = new Array()

while(a.pop()){}

while(a.shift()){}

You have called the function random2 inside the push method. So random2 method first inserts the values in the array x and returns the default value undefined (Reference), which in turn gets pushed into the array. Hence the value.

answered Nov 16 '18 at 13:28

Vignesh Raja

3,02211121

Thank you. That's correct, couldn't realise that first but thank to Nina, helped me realise that.

– uhbc
Nov 16 '18 at 13:33

1

Glad you got it. :)

– Vignesh Raja
Nov 16 '18 at 13:34

@uhbc Out of the context, isn't it should be random(a,b) inside random2 method, assuming you need to create min number of random numbers between min and max values ?

– Vignesh Raja
Nov 16 '18 at 13:44

add a comment |

Set the length to zero

x.length = 0;

answered Nov 16 '18 at 13:17

Josef Fazekas

30037

add a comment |

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3 Answers
3

active

oldest

votes

3 Answers
3

active

oldest

votes

You need not to puish the function call, which returns undefined, but just call the function random2, because the function itselft add the elements to the array.

function random(min, max) {

    return Math.floor(Math.random() * (min - max)) + min;

}



function random2(a, b) {

    for (let i = 0; i < a; i++) {

        x.push(random(0, b));

    }

}



var x = ;



random2(5, 100);

console.log(x);



x.length = 0;          // better performance than x.splice(0, x.length)

random2(5,100);        // call without using push

console.log(x);        // no undefined anymore

A better approach is to return an array in random2, because this function does not access an outer defined array. To push the values, you could take the spread syntax.

function random(min, max) {

    return Math.floor(Math.random() * (min - max)) + min;

}



function random2(a, b) {

    return Array.from({ length: a }, _ => random(0, b));

}



var x = random2(5, 100);

console.log(x);



x.length = 0;          

x.push(...random2(5, 100));

console.log(x);

edited Nov 16 '18 at 13:30

answered Nov 16 '18 at 13:22

Nina Scholz

196k15109179

After 3h of sleep haven't thought of it, thanks

– uhbc
Nov 16 '18 at 13:26

@nina, Out of the context, isn't it should be random(a,b) inside random2 method, assuming the OP need to create min number of random numbers between min and max values ? Even the OP is wrong in his implementation.

– Vignesh Raja
Nov 16 '18 at 13:40

@VigneshRaja, please ask op.

– Nina Scholz
Nov 16 '18 at 13:42

add a comment |

You need not to puish the function call, which returns undefined, but just call the function random2, because the function itselft add the elements to the array.

function random(min, max) {

    return Math.floor(Math.random() * (min - max)) + min;

}



function random2(a, b) {

    for (let i = 0; i < a; i++) {

        x.push(random(0, b));

    }

}



var x = ;



random2(5, 100);

console.log(x);



x.length = 0;          // better performance than x.splice(0, x.length)

random2(5,100);        // call without using push

console.log(x);        // no undefined anymore

A better approach is to return an array in random2, because this function does not access an outer defined array. To push the values, you could take the spread syntax.

function random(min, max) {

    return Math.floor(Math.random() * (min - max)) + min;

}



function random2(a, b) {

    return Array.from({ length: a }, _ => random(0, b));

}



var x = random2(5, 100);

console.log(x);



x.length = 0;          

x.push(...random2(5, 100));

console.log(x);

edited Nov 16 '18 at 13:30

answered Nov 16 '18 at 13:22

Nina Scholz

196k15109179

After 3h of sleep haven't thought of it, thanks

– uhbc
Nov 16 '18 at 13:26

@nina, Out of the context, isn't it should be random(a,b) inside random2 method, assuming the OP need to create min number of random numbers between min and max values ? Even the OP is wrong in his implementation.

– Vignesh Raja
Nov 16 '18 at 13:40

@VigneshRaja, please ask op.

– Nina Scholz
Nov 16 '18 at 13:42

add a comment |

You need not to puish the function call, which returns undefined, but just call the function random2, because the function itselft add the elements to the array.

function random(min, max) {

    return Math.floor(Math.random() * (min - max)) + min;

}



function random2(a, b) {

    for (let i = 0; i < a; i++) {

        x.push(random(0, b));

    }

}



var x = ;



random2(5, 100);

console.log(x);



x.length = 0;          // better performance than x.splice(0, x.length)

random2(5,100);        // call without using push

console.log(x);        // no undefined anymore

A better approach is to return an array in random2, because this function does not access an outer defined array. To push the values, you could take the spread syntax.

function random(min, max) {

    return Math.floor(Math.random() * (min - max)) + min;

}



function random2(a, b) {

    return Array.from({ length: a }, _ => random(0, b));

}



var x = random2(5, 100);

console.log(x);



x.length = 0;          

x.push(...random2(5, 100));

console.log(x);

edited Nov 16 '18 at 13:30

answered Nov 16 '18 at 13:22

Nina Scholz

196k15109179

You need not to puish the function call, which returns undefined, but just call the function random2, because the function itselft add the elements to the array.

function random(min, max) {

    return Math.floor(Math.random() * (min - max)) + min;

}



function random2(a, b) {

    for (let i = 0; i < a; i++) {

        x.push(random(0, b));

    }

}



var x = ;



random2(5, 100);

console.log(x);



x.length = 0;          // better performance than x.splice(0, x.length)

random2(5,100);        // call without using push

console.log(x);        // no undefined anymore

A better approach is to return an array in random2, because this function does not access an outer defined array. To push the values, you could take the spread syntax.

function random(min, max) {

    return Math.floor(Math.random() * (min - max)) + min;

}



function random2(a, b) {

    return Array.from({ length: a }, _ => random(0, b));

}



var x = random2(5, 100);

console.log(x);



x.length = 0;          

x.push(...random2(5, 100));

console.log(x);

function random(min, max) {

    return Math.floor(Math.random() * (min - max)) + min;

}



function random2(a, b) {

    for (let i = 0; i < a; i++) {

        x.push(random(0, b));

    }

}



var x = ;



random2(5, 100);

console.log(x);



x.length = 0;          // better performance than x.splice(0, x.length)

random2(5,100);        // call without using push

console.log(x);        // no undefined anymore

function random(min, max) {

    return Math.floor(Math.random() * (min - max)) + min;

}



function random2(a, b) {

    for (let i = 0; i < a; i++) {

        x.push(random(0, b));

    }

}



var x = ;



random2(5, 100);

console.log(x);



x.length = 0;          // better performance than x.splice(0, x.length)

random2(5,100);        // call without using push

console.log(x);        // no undefined anymore

function random(min, max) {

    return Math.floor(Math.random() * (min - max)) + min;

}



function random2(a, b) {

    return Array.from({ length: a }, _ => random(0, b));

}



var x = random2(5, 100);

console.log(x);



x.length = 0;          

x.push(...random2(5, 100));

console.log(x);

function random(min, max) {

    return Math.floor(Math.random() * (min - max)) + min;

}



function random2(a, b) {

    return Array.from({ length: a }, _ => random(0, b));

}



var x = random2(5, 100);

console.log(x);



x.length = 0;          

x.push(...random2(5, 100));

console.log(x);

edited Nov 16 '18 at 13:30

answered Nov 16 '18 at 13:22

Nina Scholz

196k15109179

edited Nov 16 '18 at 13:30

answered Nov 16 '18 at 13:22

Nina Scholz

196k15109179

answered Nov 16 '18 at 13:22

Nina Scholz

196k15109179

answered Nov 16 '18 at 13:22

Nina Scholz

196k15109179

After 3h of sleep haven't thought of it, thanks

– uhbc
Nov 16 '18 at 13:26

@nina, Out of the context, isn't it should be random(a,b) inside random2 method, assuming the OP need to create min number of random numbers between min and max values ? Even the OP is wrong in his implementation.

– Vignesh Raja
Nov 16 '18 at 13:40

@VigneshRaja, please ask op.

– Nina Scholz
Nov 16 '18 at 13:42

add a comment |

After 3h of sleep haven't thought of it, thanks

– uhbc
Nov 16 '18 at 13:26

@nina, Out of the context, isn't it should be random(a,b) inside random2 method, assuming the OP need to create min number of random numbers between min and max values ? Even the OP is wrong in his implementation.

– Vignesh Raja
Nov 16 '18 at 13:40

@VigneshRaja, please ask op.

– Nina Scholz
Nov 16 '18 at 13:42

After 3h of sleep haven't thought of it, thanks

– uhbc
Nov 16 '18 at 13:26

@nina, Out of the context, isn't it should be random(a,b) inside random2 method, assuming the OP need to create min number of random numbers between min and max values ? Even the OP is wrong in his implementation.

– Vignesh Raja
Nov 16 '18 at 13:40

@VigneshRaja, please ask op.

– Nina Scholz
Nov 16 '18 at 13:42

add a comment |

To empty an array, there are multiple ways as explained here with some benchmark results and explanation regarding their performance.

As an aggregation, asssume var a = [1,2,3,4,5]

a =

a.length = 0

a.splice(0, a.length)

a = new Array()

while(a.pop()){}

while(a.shift()){}

answered Nov 16 '18 at 13:28

Vignesh Raja

3,02211121

Thank you. That's correct, couldn't realise that first but thank to Nina, helped me realise that.

– uhbc
Nov 16 '18 at 13:33

1

Glad you got it. :)

– Vignesh Raja
Nov 16 '18 at 13:34

@uhbc Out of the context, isn't it should be random(a,b) inside random2 method, assuming you need to create min number of random numbers between min and max values ?

– Vignesh Raja
Nov 16 '18 at 13:44

add a comment |

To empty an array, there are multiple ways as explained here with some benchmark results and explanation regarding their performance.

As an aggregation, asssume var a = [1,2,3,4,5]

a =

a.length = 0

a.splice(0, a.length)

a = new Array()

while(a.pop()){}

while(a.shift()){}

answered Nov 16 '18 at 13:28

Vignesh Raja

3,02211121

Thank you. That's correct, couldn't realise that first but thank to Nina, helped me realise that.

– uhbc
Nov 16 '18 at 13:33

1

Glad you got it. :)

– Vignesh Raja
Nov 16 '18 at 13:34

@uhbc Out of the context, isn't it should be random(a,b) inside random2 method, assuming you need to create min number of random numbers between min and max values ?

– Vignesh Raja
Nov 16 '18 at 13:44

add a comment |

To empty an array, there are multiple ways as explained here with some benchmark results and explanation regarding their performance.

As an aggregation, asssume var a = [1,2,3,4,5]

a =

a.length = 0

a.splice(0, a.length)

a = new Array()

while(a.pop()){}

while(a.shift()){}

answered Nov 16 '18 at 13:28

Vignesh Raja

3,02211121

To empty an array, there are multiple ways as explained here with some benchmark results and explanation regarding their performance.

As an aggregation, asssume var a = [1,2,3,4,5]

a =

a.length = 0

a.splice(0, a.length)

a = new Array()

while(a.pop()){}

while(a.shift()){}

answered Nov 16 '18 at 13:28

Vignesh Raja

3,02211121

answered Nov 16 '18 at 13:28

Vignesh Raja

3,02211121

answered Nov 16 '18 at 13:28

Vignesh Raja

3,02211121

answered Nov 16 '18 at 13:28

Vignesh Raja

3,02211121

Thank you. That's correct, couldn't realise that first but thank to Nina, helped me realise that.

– uhbc
Nov 16 '18 at 13:33

1

Glad you got it. :)

– Vignesh Raja
Nov 16 '18 at 13:34

@uhbc Out of the context, isn't it should be random(a,b) inside random2 method, assuming you need to create min number of random numbers between min and max values ?

– Vignesh Raja
Nov 16 '18 at 13:44

add a comment |

Thank you. That's correct, couldn't realise that first but thank to Nina, helped me realise that.

– uhbc
Nov 16 '18 at 13:33

1

Glad you got it. :)

– Vignesh Raja
Nov 16 '18 at 13:34

@uhbc Out of the context, isn't it should be random(a,b) inside random2 method, assuming you need to create min number of random numbers between min and max values ?

– Vignesh Raja
Nov 16 '18 at 13:44

Thank you. That's correct, couldn't realise that first but thank to Nina, helped me realise that.

– uhbc
Nov 16 '18 at 13:33

Glad you got it. :)

– Vignesh Raja
Nov 16 '18 at 13:34

@uhbc Out of the context, isn't it should be random(a,b) inside random2 method, assuming you need to create min number of random numbers between min and max values ?

– Vignesh Raja
Nov 16 '18 at 13:44

add a comment |

Set the length to zero

x.length = 0;

answered Nov 16 '18 at 13:17

Josef Fazekas

30037

add a comment |

Set the length to zero

x.length = 0;

answered Nov 16 '18 at 13:17

Josef Fazekas

30037

add a comment |

Set the length to zero

x.length = 0;

answered Nov 16 '18 at 13:17

Josef Fazekas

30037

Set the length to zero

x.length = 0;

answered Nov 16 '18 at 13:17

Josef Fazekas

30037

answered Nov 16 '18 at 13:17

Josef Fazekas

30037

answered Nov 16 '18 at 13:17

Josef Fazekas

30037

answered Nov 16 '18 at 13:17

Josef Fazekas

30037

add a comment |

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