javascript - 如何在正则表达式中使用变量？(How do you use a variable in a regular expression?)

Question

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.(我想在JavaScript中创建String.replaceAll()方法，并且我认为使用正则表达式是最简洁的方法。)

However, I can't figure out how to pass a variable in to a regex.(但是，我不知道如何将变量传递给正则表达式。) I can do this already which will replace all the instances of "B" with "A" .(我已经可以这样做了，它将用"A"替换"B"所有实例。)

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

But I want to do something like this:(但是我想做这样的事情：)

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

But obviously this will only replace the text "replaceThis" ...so how do I pass this variable in to my regex string?(但是显然，这只会替换文本"replaceThis" ...所以如何将这个变量传递给我的正则表达式字符串？)

  ask by JC Grubbs translate from so

Answer 1

Instead of using the /regex/g syntax, you can construct a new RegExp object:(您可以构造一个新的RegExp对象， /regex/g使用/regex/g语法：)

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

You can dynamically create regex objects this way.(您可以通过这种方式动态创建正则表达式对象。)

Then you will do:(然后，您将执行以下操作：)

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