How to escape regular expression in javascript ?

Question

My codes is like

pattern = 'arrayname[1]'; // fetch from dom, make literal here just for example
reg = new RegExp(RegExp.quote(pattern), 'g');
mystring.replace(reg, 'arrayname[2]');

But it just cannot get running with error message says: "RegExp.quote is not a function", am i missing something simple?

Answer 1

This question got me searching on Google for a RegEx.quote function in JavaScript, which I was not aware of. It turns out that the function exists in only one place, namely in an answer by Gracenote here on StackOverflow. The function is defined like this:

RegExp.quote = function(str) {
    return str.replace(/([.?*+^$[\]\\(){}-])/g, "\\$1");
};

If you wish to use this function, you will need to include the above definition somewhere above the point where you use the function in your script.

Answer 2

Well, first of all you can define the regular expression with its own constant syntax:

var reg = /arrayname\[1\]/;

Inside the regular expression you quote things with backslash. Now, if you're starting from a string, you have to "protect" those backslashes inside the string constant. In that case, the pattern is being parsed twice: once when the string constant is gobbled by the Javascript parser, and then once by the RegExp constructor:

var pattern = "arrayname\\[1\\]";
var reg = new RegExp(pattern);

The backslashes are doubled so that the string "pattern" will look like the regular expression in my first example - one backslash before each bracket character.

Answer 3

If you're replacing literally, you don't need a regexp in the first place:

 str = str.split(search).join(replace)