从字符串中提取（“获取”）一个数字

问题描述

我在javascript中有一个字符串，如`＃box2'，我只想要它的'2'。

I have a string in javascript like `#box2' and I just want the '2' from it.

尝试：

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

它仍会在警报中返回＃box2，我该如何让它工作？

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

它需要适应最后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

对于这个具体的例子，

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

：

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

由于这个答案因某些原因而受到欢迎，这里有一个奖励：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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