javaScript-查找给定整数的所有除数的总和 [英] javaScript - Find the sum of all divisors of a given integer

问题描述

我正在做一些编码练习，但我无法解决这个问题.

i'm doing some coding exercises and i'm not being able to solve this one.

查找给定整数的所有除数之和.对于n = 12，输入应为sumOfDivisors(n)= 28.

Find the sum of all divisors of a given integer. For n = 12, the input should be sumOfDivisors(n) = 28.

例如:1 + 2 + 3 + 4 + 6 + 12 = 28.

example: 1 + 2 + 3 + 4 + 6 + 12 = 28.

约束:1≤n≤15.

我该如何解决这个问题?我无法.

how can i solve this exercise? i'm not being able to.

function(n){
    var arr = [],
        finalSum;

    if(n <= 1 || n => 16){
       return false ;   
   }
   for(var i = 0; i < n; i++){
       var tmp= n/2;
       arr.push(tmp)    
       // i need to keep on dividing n but i can't get the way of how to
   }
  return finalSum;
}

推荐答案

这是另一种方法:

var divisors = n=>[...Array(n+1).keys()].slice(1)
   .reduce((s, a)=>s+(!(n % a) && a), 0);

console.log(divisors(12));

JSFiddle: https://jsfiddle.net/32n5jdnb/141/

JSFiddle: https://jsfiddle.net/32n5jdnb/141/

说明:

• n => 这是一个箭头函数，等效于function(n){.如果只有一个参数，则不需要().
• Array(n + 1)创建一个由n + 1个元素组成的空数组
• .keys()获取空数组的键(索引，即0、1、2)，这是创建数字序列的一种方法
• [... Array(n + 1)].keys()] 使用spread(...)运算符将迭代器转换为另一个数组，从而使用数字序列创建一个数组
• .slice(1)删除第一个元素，从而创建一个以1开头的序列.还记得n + 1吗?
• .reduce()是一种遍历每个元素并计算值以将数组缩减为一个值的方法.它接收一个回调函数作为参数，以计算计算的值和初始值
• (s，a)=> 是reduce的回调函数.这是一个箭头函数，等效于函数{s，a} {
• s +(！(n％a)&& a)是该值的计算.
• s + s(用于求和)或最后计算的值+
• ！(n％a)仅对具有0作为模数值的元素返回true.
• (！(n％a)&& a)是js技巧".情况是javascript中的布尔表达式不返回true或false.它们返回真实"或虚假"值，然后将其转换为布尔值.因此，实际的返回值是&&(考虑到两者都必须是真实的)和||的第一个thothy值.(只考虑一个事实).因此，这基本上意味着:如果 a 是一个模块化值(即！= 0)，则返回 a 加上总和，否则返回0.
• ，0 是归约计算的初始值.

• n=> this is an arrow function, the equivalent to function(n) {. You don't need the () if there's only one parameter.
• Array(n+1) creates an empty array of n+1 elements
• .keys() gets the keys of the empty array (the indexes i.e. 0, 1, 2) so this is a way to create a numeric sequence
• [...Array(n+1)].keys()] uses the spread (...) operator to transform the iterator in another array so creating an array with the numeric sequence
• .slice(1) removes the first element thus creating a sequence starting with 1. Remember the n+1 ?
• .reduce() is a method that iterates though each element and calculates a value in order to reduce the array to one value. It receives as parameter a callback function to calculate the value and the initial value of the calculation
• (s, a)=> is the callback function for reduce. It's an arrow function equivalent to function(s, a) {
• s+(!(n % a) && a) is the calculation of the value.
• s+ s (for sum) or the last value calculated +
• !(n % a) this returns true only for the elements that have a 0 as modular value.
• (!(n % a) && a) is a js 'trick'. The case is that boolean expressions in javascript don't return true or false. They return a 'truthy' or 'falsy' value which is then converted to boolean. So the actual returned value is the right value for && (considering both have to be truthy) and the first thuthy value found for || (considering only one need to be truthy). So this basically means: if a is a modular value (i.e. != 0) return a to add to the sum, else return 0.
• , 0 is the initial value for the reduce calculation.

减少文档: https://developer.mozilla.org/pt-BR/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce

修改

向特里斯坦前进的答案:

Answering to Tristan Forward:

var divisorsList = [];
var divisors = (n)=>[...Array(n+1).keys()].slice(1)
       .reduce((s, a)=>{
          var divisor = !(n % a) && a;
          if (divisor) divisorsList.push(divisor);
          return s+divisor;
       }, 0);
    

console.log('Result:', divisors(12));
console.log('Divisors:', divisorsList);

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