如何从JavaScript中的字符串中提取数字? [英] How can I extract a number from a string in JavaScript?

问题描述

我在JavaScript中有一个字符串(例如#box2)，我只想从中获得2.

I have a string in JavaScript (e.g #box2) and I just want the 2 from it.

我尝试过:

var thestring = $(this).attr('href');
var thenum = thestring.replace( /(^.+)(\w\d+\w)(.+$)/i,'$2');
alert(thenum);

它仍然在警报中返回#box2，如何使它正常工作?

It still returns #box2 in the alert, how can I get it to work?

它需要容纳结尾处附加的任何长度数字.

It needs to accommodate for any length number attached on the end.

推荐答案

对于此特定示例，

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

在一般情况下:

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

由于这个答案由于某种原因而受到欢迎，因此有一个好处:正则表达式生成器.

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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