Sum of the arrays, calculating the sums of all the elements in the given array of arr

One, the problem analysis: can use the aggregation method of the array to calculate, reduce and reduceright. The two functions are almost identical. Just merge in the opposite direction. Both reduce and reduceright can receive two parameters. The first is a function called on each item, and the second is the initial value of the merge base.

Two, solve the problem.

function sum (arr) {

var sum=0;

if (Array.prototype.reduce) {

sum = arr.reduce (function (Prev,cur,index,arr) {

return prev+cur;

});

return sum;

}

else {

for (Var i=0;i<arr.length;i++) {

Sum+=arr[i];
}
return sum;

}

};

Sum of the arrays, calculating the sums of all the elements in the given array of arr