求和一个数字的所有数字 Javascript
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Sum all the digits of a number Javascript
提问by Hodorogea Alexandru
I am newbie.
我是新手。
I want to make small app which will calculate the sum of all the digits of a number.
我想制作一个小应用程序来计算一个数字的所有数字的总和。
For example, if I have the number 2568, the app will calculate 2+5+6+8 which is equal with 21. Finally, it will calculate the sum of 21's digits and the final result will be 3 .
例如，如果我有数字 2568，应用程序将计算 2+5+6+8 等于 21。最后，它会计算 21 的数字之和，最终结果为 3 。
Please help me
请帮我
回答by Federico Antonucci
How about this simple approach using modulo 9 arithmetic?
这种使用模 9 算术的简单方法怎么样？
function sumDigits(n) {
return (n - 1) % 9 + 1;
}
回答by Nina Scholz
Basically you have two methods to get the sum of all parts of an integer number.
基本上你有两种方法来获得一个整数的所有部分的总和。
With numerical operations
Take the number and build the remainder of ten and add that. Then take the integer part of the division of the number by 10. Proceed.
用数值运算
取数字并建立十的余数并将其相加。然后取数字除以 10 的整数部分。继续。
var value = 2568,
sum = 0;
while (value) {
sum += value % 10;
value = Math.floor(value / 10);
}
console.log(sum);Use string operations
Convert the number to string, split the string and get an array with all digits and perform a reduce for every part and return the sum.
使用字符串操作
将数字转换为字符串，拆分字符串并获得一个包含所有数字的数组，并对每个部分执行归约并返回总和。
var value = 2568,
sum = value
.toString()
.split('')
.map(Number)
.reduce(function (a, b) {
return a + b;
}, 0);
console.log(sum);For returning the value, you need to addres the valueproperty.
要返回值，您需要添加value属性。
rezultat.value = sum;
// ^^^^^^
function sumDigits() {
var value = document.getElementById("thenumber").value,
sum = 0;
while (value) {
sum += value % 10;
value = Math.floor(value / 10);
}
var rezultat = document.getElementById("result");
rezultat.value = sum;
}<input type="text" placeholder="number" id="thenumber"/><br/><br/>
<button onclick="sumDigits()">Calculate</button><br/><br/>
<input type="text" readonly="true" placeholder="the result" id="result"/>回答by Konard
The sum of digits can be calculated using that function (based on other answers):
可以使用该函数计算数字总和（基于其他答案）：
function sumDigits(n) {
let sum = 0;
while (n) {
digit = n % 10;
sum += digit;
n = (n - digit) / 10;
}
return sum;
}
If you really need to sum the digits recursively there is recursive version of the function:
如果您确实需要递归地求和数字，则可以使用该函数的递归版本：
function sumDigitsRecursively(n) {
let sum = sumDigits(n);
if (sum < 10)
return sum;
else
return sumDigitsRecursively(sum);
}
The sumDigitsRecursively(2568)expression will be equal to 3. Because 2+5+6+8 = 21and 2+1 = 3.
的sumDigitsRecursively(2568)表达将等于3。因为2+5+6+8 = 21和2+1 = 3。
Note that recursive solutionby @FedericoAntonucci should be more efficient, but it does not give you intermediate sum of digits if you need it.
请注意，@FedericoAntonucci 的递归解决方案应该更有效，但如果您需要，它不会为您提供中间数字总和。
