Question

// I am trying to make a clone of String's replace function
// and then re-define the replace function (with a mind to
// call the original from the new one with some mods)
String.prototype.replaceOriginal = String.prototype.replace
String.prototype.replace = {}

This next line is now broken – how do I fix?

"lorem ipsum".replaceOriginal(/(orem |um)/g,'')

Answer 1

The only possible issue is that your code is executed twice, which causes problems: The real original .replace will disappear.

To avoid such problems, I strongly recommend to replace built-in methods using the following general method:

(function(replace) {                         // Cache the original method
    String.prototype.replace = function() {  // Redefine the method
        // Extra function logic here
        var one_plus_one = 3;
        // Now, call the original method
        return replace.apply(this, arguments);
    };
})(String.prototype.replace);

• This allows multiple method modifications without breaking existing functionality
• The context is preserved by .apply(): Usually, the this object is vital for (prototype) methods.