Question 246443 in Html Question posted in
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Html – regex expression to find 10 or 100,1000…doesn't work

I create the regex /(10?|10{2,})/g to find 1,10 or 100,1000… but the code below doesn’t return the expected result. I don’t know where I went wrong, please help me!

<!DOCTYPE html>
<html>
<body>

<h2>JavaScript Regular Expressions</h2>

<p>Do a global search for a "1", followed by zero or one "0" characters:</p>

<p id="demo"></p>

<script>
let text = "1, 10, 100 or 1000?";
let result = text.match(/(10?|10{2,})/g);
//should return 1,10,100,1000 but instead return 1,10,10,10
document.getElementById("demo").innerHTML = result;
</script>

</body>
</html>
Tags:

2

Answers


  1. 0

    Your issue is that 10? will match all the 1, 10, 100, 1000 in your string, and since that is the first element in the alternation, the regex engine stops when it matches (and so your longest match is 10). You could solve that by swapping the alternation around so that the longest match is first:

    <!DOCTYPE html>
<html>
<body>

<h2>JavaScript Regular Expressions</h2>

<p>Do a global search for a "1", followed by zero or one "0" characters:</p>

<p id="demo"></p>

<script>
let text = "1, 10, 100 or 1000?";
let result = text.match(/10{2,}|10?/g);
document.getElementById("demo").innerHTML = result;
</script>

</body>
</html>

    But better yet, just simplify the regex to 10* (1 followed by 0 or more 0s):

    <!DOCTYPE html>
<html>
<body>

<h2>JavaScript Regular Expressions</h2>

<p>Do a global search for a "1", followed by zero or one "0" characters:</p>

<p id="demo"></p>

<script>
let text = "1, 10, 100 or 1000?";
let result = text.match(/10*/g);
document.getElementById("demo").innerHTML = result;
</script>

</body>
</html>

    Note also that you don’t need a capturing group (...) in your regex as you are only interested in the whole match.

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  2. 0

    I will add.

    Search substrings:

    let text = "1, 10, 100 or 1000 (3100, 10000, 1000000)?";
let result = text.match(/10{1,3}/g);

    Output:

    10,100,1000,100,1000,1000

    Search words only on pattern:

    let text = "1, 10, 100 or 1000 (3100, 10000, 1000000)?";
let result = text.match(/b10{1,3}b/g);

    Output:

    10,100,1000

    Search words only on pattern 1 and more zeroes:

    let text = "1, 10, 100 or 1000 (3100, 10000, 1000000)?";
let result = text.match(/b10{1,}b/g);

    Output:

    10,100,1000,10000,1000000

    Find words ending in a pattern of 1 or more zeros:

    let text = "1, 10, 100 or 1000 (3100, 10000, 1000000)?";
let result = text.match(/bw*10{1,}b/g);

    Output:

    10,100,1000,3100,10000,1000000

    Finds words ending only in a pattern of 1 or more zeros:

    let text = "1, 10, 100 or 1000 (3100, 10000, 1000000)?";
let result = text.match(/bw+10{1,}b/g);

    Output:

    3100
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