Web/JavaScript/Reference/Global objects/RegExp/@@replace

The [@@replace]() method replaces some or all matches of a this pattern in a string by a replacement, and returns the result of the replacement as a new string. The replacement can be a string or a function to be called for each match.

Syntax

regexp[Symbol.replace](str, newSubStr|function)

Parameters

str: A String that is a target of the replacement.
newSubStr (replacement): The String that replaces the substring. A number of special replacement patterns are supported; see the Specifying a string as a parameter section in String.prototype.replace() page.
function (replacement): A function to be invoked to create the new substring. The arguments supplied to this function are described in the Specifying a function as a parameter section in String.prototype.replace() page.

Return value

A new string with some or all matches of a pattern replaced by a replacement.

Description

This method is called internally in String.prototype.replace() if the pattern argument is a RegExp object. For example, following two examples return same result.

'abc'.replace(/a/, 'A');

/a/[Symbol.replace]('abc', 'A');

This method exists for customizing replace behavior in RegExp subclass.

If pattern argument is not a RegExp object, String.prototype.replace() doesn't call this method, nor creates a RegExp object.

Examples

Direct call

This method can be used in almost the same way as String.prototype.replace(), except the different this and the different arguments order.

var re = /-/g; 
var str = '2016-01-01';
var newstr = re[Symbol.replace](str, '.');
console.log(newstr);  // 2016.01.01

Using @@replace in subclasses

Subclasses of RegExp can override the [@@replace]() method to modify the default behavior.

class MyRegExp extends RegExp {
  constructor(pattern, flags, count) {
    super(pattern, flags);
    this.count = count;
  }
  [Symbol.replace](str, replacement) {
    // Perform @@replace |count| times.
    var result = str;
    for (var i = 0; i < this.count; i++) {
      result = RegExp.prototype[Symbol.replace].call(this, result, replacement);
    }
    return result;
  }
}

var re = new MyRegExp('\\d', '', 3);
var str = '01234567';
var newstr = str.replace(re, '#'); // String.prototype.replace calls re[@@replace].
console.log(newstr); // ###34567

Specifications

Specification

ECMAScript (ECMA-262)The definition of 'RegExp.prototype[@@replace' in that specification.]

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
`@@replace`	Chrome Full support 50	Edge Full support 79	Firefox Full support 49	IE No support No	Opera Full support 37	Safari Full support 10	WebView Android Full support 50	Chrome Android Full support 50	Firefox Android Full support 49	Opera Android Full support 37	Safari iOS Full support 10	Samsung Internet Android Full support 5.0	nodejs Full support 6.0.0

Legend

Full support: Full support
No support: No support