How can I extract a number from a string in JavaScript? How can I extract a number from a string in JavaScript? javascript javascript

How can I extract a number from a string in JavaScript?


javascript regex string numbers

For this specific example,

 var thenum = thestring.replace( /^\D+/g, ''); // replace all leading non-digits with nothing

in the general case:

 thenum = "foo3bar5".match(/\d+/)[0] // "3"

Since this answer gained popularity for some reason, here's a bonus: regex generator.

function getre(str, num) {  if(str === num) return 'nice try';  var res = [/^\D+/g,/\D+$/g,/^\D+|\D+$/g,/\D+/g,/\D.*/g, /.*\D/g,/^\D+|\D.*$/g,/.*\D(?=\d)|\D+$/g];  for(var i = 0; i < res.length; i++)    if(str.replace(res[i], '') === num)       return 'num = str.replace(/' + res[i].source + '/g, "")';  return 'no idea';};function update() {  $ = function(x) { return document.getElementById(x) };  var re = getre($('str').value, $('num').value);  $('re').innerHTML = 'Numex speaks: <code>' + re + '</code>';}
<p>Hi, I'm Numex, the Number Extractor Oracle.<p>What is your string? <input id="str" value="42abc"></p><p>What number do you want to extract? <input id="num" value="42"></p><p><button onclick="update()">Insert Coin</button></p><p id="re"></p>
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