String manipulation functions (and polyfills) - to be used with RequireJS

string.js

"use strict";
//String functions
define([], function() {
    var addFunctionToString = function(name, value) {
        if(!String.prototype.hasOwnProperty(name)) {
            Object.defineProperty(String.prototype, name, {
                enumerable: false,
                configurable: false,
                writable: false,
                value: value
            });
        }
    };
    
    // Format a string: "Hello {0}, it's {1} o'clock".format("world", 5) -> hello world, it's 5 o'clock
    addFunctionToString('format', function() {
        var args = arguments;
        return this.replace(/{(\d+)}/g, function(match, number) { 
            return (typeof args[number] !== 'undefined') ? args[number] : match;
        });
    });
    
    // Ellipsise a long string
    // toLength is the max length of the result
    // where is one of ['front','middle','end'] -- default is 'end'
    // ellipsis is the character used -- default is ...
    addFunctionToString('ellipsise', function(toLength, where, ellipsis) {
        if (toLength < 1 || this.length < toLength) return this.toString();
        ellipsis = ellipsis || '\u2026';
        switch (where) {
            case 'front':
                return ellipsis + this.substr(this.length - toLength);
                break;
            case 'middle':
                return this.substr(0, toLength / 2) + ellipsis + this.substr(this.length - toLength / 2);
                break;
            case 'end':
            default:
                return this.substr(0, toLength) + ellipsis;
                break;
        }
    });
    
    // Returns true if a string starts with the search string
    // optional: search start position
    addFunctionToString('startsWith', function(searchString, position) {
        position = position || 0;
        return this.indexOf(searchString, position) === position;
    });
    
    // Returns true if a string ends with the search string
    // optional: search end position
    addFunctionToString('endsWith', function(searchString, position) {
        position = position || this.length;
        position = position - searchString.length;
        return this.lastIndexOf(searchString) === position;
    });
});