1、遍历求值
function sum(arr){
var result = 0;
for(var i=0;i<arr.length;i++){
result += arr[i]
}
return result;
}
2、Array.reduce()
function sum(arr){
return arr.reduce(function(prev, curr, idx, arr){
return prev + curr;
});
}
3、forEach()
function sum(arr){
var result = 0;
arr.forEach(function(arr) {
result+= arr;
});
return result;
}