Adding a String format function similar to C's printf to the String prototype and String object

addStringFormat.js

// implementation of format function on the String prototype
// this is similar to printf() in C
// First, checks if it isn't implemented yet.
if (!String.prototype.format) {
  String.prototype.format = function() {
    var args = arguments;
    return this.replace(/{(\d+)}/g, function(match, number) { 
      return typeof args[number] != 'undefined'
        ? args[number]
        : match
      ;
    });
  };
}

// adding a method to String
if (!String.format) {
  String.format = function(format) {
    var args = Array.prototype.slice.call(arguments, 1);
    return format.replace(/{(\d+)}/g, function(match, number) { 
      return typeof args[number] != 'undefined'
        ? args[number] 
        : match
      ;
    });
  };
}

AddStringFormat_README.md

String format function

Similar to C's printf()

Usage

Using prototype format function

"I'm the god damn {0}{1}".format("Batman", "!");
// returns I'm the god damn Batman!

Using String's format function

String.format("And I can call my god damn {0} whetever I {1} {2}", "car", "want");
// returns And I can call my god damn car whetever I want {2}

Reference

• http://stackoverflow.com/questions/610406/javascript-equivalent-to-printf-string-format