Fastest method to replace all instances of a character in a string

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");

Stack Overflow Q#2116558, score: 1320