Get friendly with the Natives

Written by Ryan Florence on 24 March 2010 – Posted under all , tips

Have you extended a Native lately? It's an incredibly helpful thing.

The Difference:

I've seen stuff like this:

fn1(fn2(10, fn3('house')));

Hard to figure out what's happening. Instead you can write code like:

fn3('house').fn2(10).fn1();

A Useful, Real Example, zeroPad

I've used this in a couple scripts, it takes a number and returns a string with zeros padded in front: 123 becomes '000123'. Really handy for filenames and the like.

Functionally Based Example

function zeroPad(num, zeros){
  zeros = zeros || 3;
  var str = '' + num;
  zeros.times(function(){ str = '0'+str; });
  return str;
};

// usage
doSomething(zeroPad(document.getElementById('myInput').value, 3));

Native Extentions Based Example

Number.implement({
  zeroPad: function(zeros){
    var str = '' + this;
    zeros.times(function(){ str = '0'+str; });
    return str;
  }
});

// so that it works on both numbers and strings
String.implement({
  zeroPad: function(zeros){
      return this.toInt().zeroPad(zeros);
  }
});

// usage
$('myInput').get('value').zeroPad(3).doSomething();

Side by Side:

doSomething(zeroPad(document.getElementById('myInput').value, 3));
// vs
$('myInput').get('value').zeroPad(3).doSomething();

Awesome? Yes.

Some say extending natives is a bad idea. Personally, I think it's awesome--but this topic is a sore spot for some.

Flippin' Sweet Array methods

Arian Stolwijk created this amazing gem: Array.Math . Code samples often tell the story faster:

[2,5,1,6].sum(); // 14
[2,5,6,2].product(3); // [6,15,18,6]
[9,12,15].quotient(3) // [3,4,5]

This is all made possible by extending the Array native, see?

Array.implement({

        sum: function(start,length){
            var sum = 0, 
                start = start ? start : 0,
                length = length ? length : this.count()-start;
            length = start ? length + 2 : length;
            for(var i=start;i<length;i++) sum += this[i];
            return sum;
        },

        product: function(p){
            var arr = $type(p) == 'array';
            return this.map(function(entity,i){
                return arr ? (entity * p[i]) : (entity * p);
            });
        },

        quotient: function(q){
            var arr = $type(q) == 'array';
            return this.map(function(entity,i){
                return arr ? (entity / q[i]) : (entity / q);
            });
        },

        // and a whole lot more awesome ...

    });

Quick Tips

  • this is the number or string, or whatever, when inside the method.
  • Return something that makes sense (usually this ).
  • You can implement several methods all in the same code block.

This is just one more great tool to help keep your code organized and readable.