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)); } }
function sum(arr) { var s = 0; for (var i=arr.length-1; i>=0; i--) { s += arr[i]; } return s; }
function sum(arr) { return arr.reduce(function(prev, curr, idx, arr){ return prev + curr; }); }
function sum(arr) { var s = 0; arr.forEach(function(val, idx, arr) { s += val; }, 0); return s; };
function sum(arr) { return eval(arr.join("+")); };
function sum(arr) { // 如果数组长度为1,直接返回第一个元素 if(arr.length === 1){ return arr[0] } return arr.reduce((acc,val)=> { return acc += val }) }
function sum(arr) { return arr.reduce((previousValue, currentValue ,index, arr) => { return previousValue + currentValue; },0); };必须改成:
function sum(arr) { return arr.reduce(function(previousValue, currentValue ,index, arr) { return previousValue + currentValue; },0); };
function sum(arr) { var s = 0; arr.forEach(function(ele) { s += ele; }); return s; } 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)); } } function sum(arr) { return arr.reduce(function(prev, curr) { return prev + curr; }); } function sum(arr) { return eval(arr.join("+")); }
/*我想到的答案: *1、常规循环 *2、forEach *3、reduce */ function add(arr){ var sum = 0, i, len; for( i = 0, len = arr.length; i < len; i+=1){ sum += arr[i]; } return sum; }function add(arr){ var sum = 0; arr.forEach( function( el ) { sum += el; }); return sum; }function add(arr){ return add.reduce( function( totle, val ){ return totle + val; }); }