javascript 数组中对象属性的总和
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Sum of object properties within an array
提问by Brandon
I have an array with properties, take the following for example:
我有一个带有属性的数组，例如以下内容：
var arrayPeople = [
{
name: 'joe',
job: 'programmer',
age: 25,
},
{
name: 'bob',
job: 'plumber',
age: 30,
};
];
I want to create a function that will return their average ages, here is what i have that is currently not working
我想创建一个函数来返回他们的平均年龄，这是我目前无法使用的
var ageAverage = function(array) {
var age = 0, average;
for (var i = 0; i < array.length; i++) {
age += array[i].age;
}
average = age / array.length;
return average;
};
What I am getting when running this function is Not A Number
运行此函数时我得到的不是数字
But what I can get to work is:
但我可以开始工作的是：
var ageAverage = function(array) {
var age = 0, average;
for (var i = 0; i < array.length; i++) {
age = array[0].age;
}
average = age / array.length;
return average;
};
The subtle difference here is that I took away the += and just made it =, and i took away the use of our variable i and just gave it the first index of the array. So in doing this, I know that the function is correctly substituting the parameter array with arrayPeople, but there is something going wrong in my for loop that is stopping i from becoming 0 and 1 (the indexes of arrayPeople).
这里的细微差别是我去掉了 += 并让它变成了 =，而我去掉了变量 i 的使用，只是给了它数组的第一个索引。因此，在这样做时，我知道该函数正确地用 arrayPeople 替换了参数数组，但是我的 for 循环中出了点问题，阻止了 i 变为 0 和 1（arrayPeople 的索引）。
P.S.I am trying to do this on my own, and I am not looking for someone to just do the problem for me, I would really appreciate just some hints on what to fix or maybe a concept I need to research the understand how to fix this problem.
PS我正在尝试自己做这件事，我不是在找人来为我解决问题，我真的很感激一些关于要修复什么的提示，或者我需要研究的概念，了解如何修复这个问题。
Thanks!!
谢谢！！
采纳答案by Alexander T.
You need initialize agevariable (var age = 0)
您需要初始化age变量 ( var age = 0)
var arrayPeople = [{
name: 'joe',
job: 'programmer',
age: 25,
}, {
name: 'bob',
job: 'plumber',
age: 30,
}];
var ageAverage = function(array) {
var age = 0,
average;
for (var i = 0; i < array.length; i++) {
age += array[i].age;
}
average = age / array.length;
return average;
};
console.log(
ageAverage(arrayPeople)
);in your variant, agevariable equals undefined, and undefined += number(for example 25) returns NaN;
在您的变体中，age变量等于undefined，并且undefined += number（例如 25）返回NaN；
also change ,to ;in this line
也更改,为 ;在这一行
from
从
for (var i = 0, i < array.length; i++) {
to
到
for (var i = 0; i < array.length; i++) {
回答by CD..
Consider using mapand reduce:
考虑使用map和reduce：
arrayPeople.
map(function(item){ return item.age; }).
reduce(function(a, b){ return a + b; }, 0) / arrayPeople.length;
Or just the reduceas @KooiInc pointed out:
或者就像reduce@KooiInc 指出的那样：
arrayPeople.reduce(function (a,b) { return a + b.age; }, 0) / arrayPeople.length;
A working Example:
一个工作示例：
var arrayPeople = [{
name: 'joe',
job: 'programmer',
age: 25,
}, {
name: 'bob',
job: 'plumber',
age: 30,
}],
average = arrayPeople.reduce(function(a, b) {
return a + b.age;
}, 0) / arrayPeople.length;
document.write(average);回答by Mouhamad Kawas
You should change the for to:
您应该将 for 更改为：
for (var i = 0; i < array.length; i++) instead of for (var i = 0, i < array.length; i++)
for (var i = 0; i < array.length; i++) 而不是 for (var i = 0, i < array.length; i++)
and give initial value to age
并赋予年龄初始值
var age=0
回答by Ricky
There's always a one-liner.
总有一个单线。
arrayPeople.reduce((a, o, i, p) => a + o.age / p.length, 0));
console.log(`${[{
name: 'joe',
job: 'programmer',
age: 25,
},
{
name: 'bob',
job: 'plumber',
age: 30,
}
].reduce((a, o, i, p) => a + o.age / p.length, 0)}%`);