RegExp exec not working in for loop snippet - Javascript

Question

Can someone help check this snippet? I'm just looping on array but the last item return false or null even its matches the pattern.

let texts = ["Invoice_001_1", "Invoice_001_2"];
var regTest = /(([a-zA-Z 0-9]+)_([0-9]+)_([0-9]+)$|[a-zA-Z ]+_([0-9]+)$)/gi;

for(var x=0; x<texts.length; x++) {
    console.log(texts[x]);
    var matchReg = regTest.exec(texts[x]);
    console.log(matchReg);
}

JSfiddle Demo

to put it simply: never ever use `regex.exec` in javascript. It's broken. Use `string.match` instead. — gog, Nov 21 '22 at 16:45

score 1 · Answer 1 · answered Nov 21 '22 at 16:47

The issue is that when using /g, js has a little gotcha, in that it tells the regexp to keep the index of the last match.The fix is to manually reset the index:

let texts = ["Invoice_001_1", "Invoice_001_2"];
var regTest = /(([a-zA-Z 0-9]+)_([0-9]+)_([0-9]+)$|[a-zA-Z ]+_([0-9]+)$)/gi;

for(var x=0; x<texts.length; x++) {
        console.log(texts[x]);
        var matchReg = regTest.exec(texts[x]);
    console.log(matchReg);
    regTest.lastIndex = 0;
}

Or to not use `/g` at all, it is not needed in this case – Dimava Nov 21 '22 at 16:47 — Dimava, Nov 21 '22 at 16:47

RegExp exec not working in for loop snippet - Javascript

1 Answers1