Vfrdtyky

lcl|NZ_AP012542.1_cds_WP_003600377.1_1 [locus_tag=LBPC_RS14705] [db_xref=GeneID:31583580] [protein=RepB family plasmid replication initiator protein] [protein_id=WP_003600377.1] [location=1..780] [gbkey=CDS]
ATGGCAAATACAATCAACAAAAAACAAAATCTGGCGATGCAGGCGTTGCTTAAACGCCAAGACTATCTTG

lcl|NZ_AP012542.1_cds_WP_016377574.1_2 [locus_tag=LBPC_RS14710] [db_xref=GeneID:31583581] [protein=DUF536 domain-containing protein] [protein_id=WP_016377574.1] [location=complement(1459..1956)] [gbkey=CDS]
ATGAGTAAGACCATCAAAGAACTTGCAGAGGAATTGAGCTTATCTAAATCTGGTATTCGTAAATATCTAA

I want to extract word after locus_tag= (only LBPC_RS14705 and LBPC_RS14710). How do I fix this regular expression?

[locus_tag][=]w+

You can use the following regular expression to match the locus_tag:

/[locus_tag=(w+)]/g;

In this expression, I have captured word characters after the "locus_tag=" and so you can access it by doing .exec(str)[1] twice to get both of the tags.

See a working example below:

const str = 

`lcl|NZ_AP012542.1_cds_WP_003600377.1_1 [locus_tag=LBPC_RS1477705] [db_xref=GeneID:31583580] [protein=RepB family plasmid replication initiator protein] [protein_id=WP_003600377.1] [location=1..780] [gbkey=CDS] ATGGCAAATACAATCAACAAAAAACAAAATCTGGCGATGCAGGCGTTGCTTAAACGCCAAGACTATCTTG



lcl|NZ_AP012542.1_cds_WP_016377574.1_2 [locus_tag=LBPC_RS14710] [db_xref=GeneID:31583581] [protein=DUF536 domain-containing protein] [protein_id=WP_016377574.1] [location=complement(1459..1956)] [gbkey=CDS] ATGAGTAAGACCATCAAAGAACTTGCAGAGGAATTGAGCTTATCTAAATCTGGTATTCGTAAATATCTAA`;



const regex = /[locus_tag=(w+)]/g;

console.log(regex.exec(str)[1]); // Run exec once to get the first match

console.log(regex.exec(str)[1]); // Run exec twice to get the second match

You can also try any of the following approaches.

Here I've assumed your locus tag has word characters as I can see. And w+ is there to match it.

Helpful link: https://javascript.info/regexp-groups

1st way

var s1 = "lcl|NZ_AP012542.1_cds_WP_003600377.1_1 [locus_tag=LBPC_RS14705] [db_xref=GeneID:31583580] [protein=RepB family plasmid replication initiator protein] [protein_id=WP_003600377.1] [location=1..780] [gbkey=CDS] ATGGCAAATACAATCAACAAAAAACAAAATCTGGCGATGCAGGCGTTGCTTAAACGCCAAGACTATCTTG";



var s2 = "lcl|NZ_AP012542.1_cds_WP_016377574.1_2 [locus_tag=LBPC_RS14710] [db_xref=GeneID:31583581] [protein=DUF536 domain-containing protein] [protein_id=WP_016377574.1] [location=complement(1459..1956)] [gbkey=CDS] ATGAGTAAGACCATCAAAGAACTTGCAGAGGAATTGAGCTTATCTAAATCTGGTATTCGTAAATATCTAA";



const regEx = /(locus_tag=(w+))/;



var locus_tag1 = s1.match(regEx)[2];

var locus_tag2 = s2.match(regEx)[2];



console.log(locus_tag1); // LBPC_RS14705

console.log(locus_tag2); // LBPC_RS14710

2nd way

var s1 = "lcl|NZ_AP012542.1_cds_WP_003600377.1_1 [locus_tag=LBPC_RS14705] [db_xref=GeneID:31583580] [protein=RepB family plasmid replication initiator protein] [protein_id=WP_003600377.1] [location=1..780] [gbkey=CDS] ATGGCAAATACAATCAACAAAAAACAAAATCTGGCGATGCAGGCGTTGCTTAAACGCCAAGACTATCTTG";



var s2 = "lcl|NZ_AP012542.1_cds_WP_016377574.1_2 [locus_tag=LBPC_RS14710] [db_xref=GeneID:31583581] [protein=DUF536 domain-containing protein] [protein_id=WP_016377574.1] [location=complement(1459..1956)] [gbkey=CDS] ATGAGTAAGACCATCAAAGAACTTGCAGAGGAATTGAGCTTATCTAAATCTGGTATTCGTAAATATCTAA";



const regEx = /(locus_tag=w+)/;



var locus_tag1 = s1.match(regEx)[0].split('=')[1];

var locus_tag2 = s2.match(regEx)[0].split('=')[1];



console.log(locus_tag1); // LBPC_RS14705

console.log(locus_tag2); // LBPC_RS14710