Research on JS summation algorithm

If you encounter a question like this.

function sum (arr) {        // sum     }

What would you do?

Anyway, my first reaction was to do so.

function sum (arr) {            var result = 0;              for (var in arr) {                + = arr[i];            }             return result;        }

But it was not until yesterday that I discovered another minimalist approach of the great God.

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

A word OK, is not very bad.

Simple interpretation.

The join function does not have to be explained, stitching the string. A join is used to stitch the incoming array into a string concatenated with the "+" sign. Then use the Eval function to calculate the stitched string.

This greatly saves memory and greatly shortens the computational time.

Research on JS summation algorithm