数组随机排序

方案一：

function randomArr1(arr,num){
		var result = [],
			len = arr.length;
			
		for(var i =0; i < len;i++){
			var t = Math.floor(Math.random() * arr.length);
			result.push(arr.splice(t,1)[0]);
		}
		
		if(num >= len) return result;
		return result.slice(0,num);
	}

方案二：	
function randomArr2(arr,num){
		var result = [],
			len = arr.length;
			
		for(var i =0; i < len;i++){
			var t = Math.floor(Math.random() * arr.length);
			result.push(arr[t]);
			
			var left = arr.slice(0,t),
				right = arr.slice(t + 1,arr.length);
				
			arr = left;
			arr.push.apply(arr,right);
		}
		
		if(num >= len) return result;
		return result.slice(0,num);
	}