underscorePractise3.js

(function() {
	var log = function(x) {console.log(x)}

	var a = [1, 2, 5, 8, 42, 21];
	var x;

	x = _.groupBy(a, function(num) {
		return num % 3; 
	});
	//log(x);

	var f = function(){};
	var mix = [1, true, 30, 'hello', null, 'test', 0, /aaa/, [], {}, false, f];
	//log(mix);

	y = _.groupBy(mix, function(ele) {
		return typeof ele;
	});
	//log(y);

	x = _.countBy(a, function(num){
		return num % 2 == 0 ? 'even' : 'odd' ;
	});
	//log(x);

	//log('before sort : '+a);
	x = _.sortBy(a);
	//log('after sort : '+x);

	var people = [
		{
			name	: 'moe', 
			age		: 40
		},
		{
			name	: 'larry',
			age		: 50
		},
		{
			name	: 'curly',
			age		: 60
		}
	];
	x = _.sortBy(people, 'name');
	//log(x);

	// groupBy by pure js
	var obj = {
		1:[],
		2:[],
		0:[]
	};
	for(var i = 0; i < a.length; i+=1) {
		var n = a[i] % 3;
		
		switch(n){
		case 1:
			obj[1].push(a[i]);
			break;
		case 2:
			obj[2].push(a[i]);
			break;
		case 0:
			obj[0].push(a[i]);
			break;
		default:
			obj['other'] = [a[i]];
		}
		
	}
	//log(obj);

	//countBy by pure js
	var obj = {
		even	: 0,
		odd		: 0
	};
	for(var i = 0; i < a.length; i++) {
		if( a[i] % 2 ) {
			obj['even'] += 1;
		} else {
			obj['odd'] += 1;
		}
	}
	//log(obj);

	// sortBy by pure js

	var a = [50, 1, 6, 21, 4, 18];
	var tmp;
	for(var i = 0, l = a.length; i < l; i++) {
		for(var j = i+1; j < l; j++) {
			if(a[i] > a[j]) {
				tmp = a[i];
				a[i] = a[j];
				a[j] = tmp;
			}
		}
	}
	//log(a);

})();