myString.replace( searchExpr, replaceExpr ) in ECMAScript 262

If searchExpr is a string, a case-sensitive search is performed, and only the first match found is replaced. To make a case-insensitive replacement or global replacement, use a regular expression for the search expression.

var sentence = "The quick brown fox and the duck jump over the lazy dog.";
var oneReplaced = sentence.replace( 'the' , '**the**' );
var allReplaced = sentence.replace( /the/gi , '**the**' );
// ** oneReplaced is "The quick brown fox and **the** duck jump over the lazy dog."
// ** allReplaced is "**the** quick brown fox and **the** duck jump over **the** lazy dog."

When searchExpr is a regular expression and replaceExpr is a string, the following substrings have special meaning:

$&

The entire matched substring.

$`

The portion of the original string that precedes the matched substring.

$'

The portion of the original string that follows the matched substring

$n

The n^th captured subexpression, where n is a single digit and $n is not followed by another digit.

$nn

The nn^th captured subexpression, where nn is a two-digit number.

$$

Replace with a literal "$"

var sentence = "The quick brown fox jumps over the lazy dog.";
var blankouts = sentence.replace( /\b([a-z])[a-z]+/gi , '$1****' );
// ** alternatedBlankouts is "T**** q**** b**** f**** j**** o**** t**** l**** d****."

If replaceExpr is a function, it will be passed the following arguments, in order:

• The substring that was matched.
• If searchExpr is a regular expression, one argument for each parentheses-captured substring in the expression will be passed.
• The next-to-last argument will be the index in the source string where the match occurred.
• The last argument passed is the entire source string.

var sourceString = "It's the end of the world as we know it, and I feel fine.";
function SwapCharacterPairs(str,sub1,sub2,index,srcString){
    return sub2+sub1;
}
var newString = sourceString.replace( /(.)(.)/g , SwapCharacterPairs );
// ** newString is "tIs't ehe dno  fht eowlr dsaw  enkwoi ,ta dnI f ee lifen.";

var prices = "Items cost stuff. Candy: $.50; Glasses: $3.75; 500 pages: $4.99";
var priceRE = /\$(\d*(\.\d{2})?)/g;
function IncreasePrice(str,price){
    // all the extra parameters that we don't need are ignored
    return '$'+Math.round(price*1.66*100)/100;
}
var newPrices = prices.replace(priceRE,IncreasePrice);
// ** newPrices is "Items cost stuff. Candy: $0.83; Glasses: $6.23; 500 pages: $8.28"