不用循环求和

[Sunny-117]

No description provided.

[yang-xianzhu]

const arr = []
// 求0~100000的和
for(let i =0;i<=100000;i++){arr.push(i)}

function getSum(arr){
return (arr[0] + arr[arr.length-1]) * arr.length / 2
}
const sum = getSum(arr)
console.log(sum)

[bearki99]

const arr = [1, 3, 5, 4, 3];
const res = arr.reduce((prev, next)=>prev+next, 0);

console.log(res);

[woailllljjjj]

function totalNumber(arr) {
    if(!arr || Object.prototype.toString.call(arr) !== '[object Array]' || arr.length === 0) {
        throw new Error('参数必须是数组,且不允许为空')
    }
    const first = arr.splice(0,1)[0]
    if(arr[0]) {
        arr[0] += first
        return totalNumber(arr)
    }else {
        return first
    }
}    
totalNumber([0,3,1,6])

[veneno-o]

function main(args){
    const len = args.length;
    if(len === 0){
        return 0;
    }
    return args[0] + main(args.slice(1));
}

[kangkang123269]

1. forEach方法

let arr = [1, 2, 3, 4, 5];
let sum = 0;
arr.forEach(function(item) {
    sum += item;
});
console.log(sum); // 输出: 15

2. reduce

let arr = [1, 2, 3, 4, 5];
let sum = arr.reduce((accumulator, currentValue) => accumulator + currentValue,0);
console.log(sum); // 输出:15

3. eval函数

let arr = [1,2,3 ,4 ,5];
let sum = eval(arr.join("+"));
console.log(sum); // 输出:15 

4. 递归

function sumArray(arr) {
    if (arr.length === 0) { // 基线条件：如果数组为空，那么总和就是0
        return 0;
    } else {
        return arr[0] + sumArray(arr.slice(1)); // 递归步骤：取数组的第一个元素并加上对剩余部分调用sumArray函数的结果
    }
}

let arr = [1, 2, 3, 4, 5];
console.log(sumArray(arr)); // 输出：15