Fastest method to replace all instances of a character in a string [duplicate]

What is the fastest way to replace all instances of a string/character in a string in JavaScript? A while, a for-loop, a regular expression?

The easiest would be to use a regular expression with g flag to replace all instances:

str.replace(/foo/g, "bar")

This will replace all occurrences of foo with bar in the string str. If you just have a string, you can convert it to a RegExp object like this:

var pattern = "foobar",
    re = new RegExp(pattern, "g");

Try this replaceAll: http://dumpsite.com/forum/index.php?topic=4.msg8#msg8

String.prototype.replaceAll = function(str1, str2, ignore) 
{
    return this.replace(new RegExp(str1.replace(/([\/\,\!\\\^\$\{\}\[\]\(\)\.\*\+\?\|\<\>\-\&])/g,"\\$&"),(ignore?"gi":"g")),(typeof(str2)=="string")?str2.replace(/\$/g,"$$$$"):str2);
} 

It is very fast, and it will work for ALL these conditions that many others fail on:

"x".replaceAll("x", "xyz");
// xyz

"x".replaceAll("", "xyz");
// xyzxxyz

"aA".replaceAll("a", "b", true);
// bb

"Hello???".replaceAll("?", "!");
// Hello!!!

Let me know if you can break it, or you have something better, but make sure it can pass these 4 tests.

var mystring = 'This is a string';
var newString = mystring.replace(/i/g, "a");

newString now is 'Thas as a strang'

Also you can try:

string.split('foo').join('bar');