How to sum arrays in JavaScript

Methods for JavaScript array summation: 1. Use recursion to continuously add and sum the array elements; 2. Use for loops to continuously add and sum the array elements; 3. Use forEach to traverse and let the array The elements are continuously added and summed; 4. Use the "eval(arr.join(" "))" statement to sum.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

JavaScript array summation

Method 1.Regardless of algorithm complexity, use recursion:

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)); } }

Method 2.Regular loop:

function sum(arr) { var s = 0; for (var i=arr.length-1; i>=0; i--) { s += arr[i]; } return s; }

Method 3.Functional programming map-reduce:

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

Method 4.forEach traversal:

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

Method 5.eval:

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

//测试输出运行结果： console.log(sum([ 1, 2, 3, 4 ]))

The following results can be obtained:

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