var a = [1,2,3,4,5,6,7,8,9,0,12,23,45,90];
a.sort(function (a,b) {
    var sign = (Math.random()>0.5) ? 1 : -1;
    return (a-b)*sign;
});

//有一个长度为100的数组，请以优雅的方式求出该数组的前10个元素之和
var b = [1,2,3,4,5,6,7,8,9,10];
var sum = b.slice(0,10).reduce(function (pre,cur) {
    return pre + cur;
},0);

var a = new Array(100);

a = a.join(",").split(",").map(function(item, index) {
    return index;
});