数组元素求和的几种方法

1.用递归做

function sum(arr) {
   var len = arr.length; if(len == 0){
return 0:
} else if (len == 1){ 
    return arr[0];
} else {
return arr[0] + sum(arr.slice(1));

2.函数式编程 map-reduce

function sum(arr) {
	return arr.reduce(function(prev, curr, idx, arr){
return prev + curr;
}); 
}

3.forEach遍历

function sum(arr) {
var s = 0;
arr.forEach(function(val, idx, arr) { s += val;}，0); return s;};

4.eval

function sum(arr) {
	return eval(arr.join("+"));
};