如何在正则表达式中使用变量？ [英] How do you use a variable in a regular expression?

问题描述

我想在JavaScript中创建一个String.replaceAll（）方法，我认为使用RegEx将是最简洁的方法。但是，我无法弄清楚如何将变量传递给RegEx。我已经可以做到这一点，它将用A替换所有B的实例。

I would like to create a String.replaceAll() method in JavaScript and I'm thinking that using a RegEx would be most terse way to do it. However, I can't figure out how to pass a variable in to a RegEx. I can do this already which will replace all the instances of "B" with "A".

"ABABAB".replace(/B/g, "A");

但我想做这样的事情：

String.prototype.replaceAll = function(replaceThis, withThis) {
    this.replace(/replaceThis/g, withThis);
};

但显然这只会替换文本replaceThis...所以如何传递这个变量在我的RegEx字符串中？

But obviously this will only replace the text "replaceThis"...so how do I pass this variable in to my RegEx string?

推荐答案

而不是使用 / regex / g 语法，您可以构建一个新的 RegExp 对象：

Instead of using the /regex/g syntax, you can construct a new RegExp object:

var replace = "regex";
var re = new RegExp(replace,"g");

您可以通过这种方式动态创建正则表达式对象。然后你会这样做：

You can dynamically create regex objects this way. Then you will do:

"mystring".replace(re, "newstring");

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