String.prototype.format = function() {
    var str = this,
        i = arguments.length;
      
    while (i--) {
        str = str.replace(new RegExp('\\{' + i + '\\}', 'gm'), arguments[i]);
    }
    return str;
};

"My Name is {0}, my Phone is {1}".format(
    Arnold,
    050
);

String.prototype.trim = function () {
    return this.replace(new RegExp(/^\s+|\s+$/g), "");
};
String.prototype.ltrim = function () {
    return this.replace(/^\s+/, "");
};
String.prototype.rtrim = function () {
    return this.replace(/\s+$/, "");
};

" space before, space after ".trim()

"this is string".replace("is", "a").replace("this", "This")

String.prototype.multiReplace = function (hash) {
    var str = this, key;

    for (key in hash) {
        if (Object.prototype.hasOwnProperty.call(hash, key)) {
            str = str.replace(key, hash[key]);
        }
    }
    return str;
};

"this is string".multiReplace({"is":"a", "this":"This"})

jQuery.fn.Exists = function () {
    return ($(this).length > 0)
}

if($("element").Exists()){
    alert("element Exists");
}