在 JavaScript 中对数组中的值求和
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Sum values from an Array in JavaScript
提问by Daniela costina Vaduva
I have defined a JavaScript variables called myDatawhich is a new Arraylike this:
我定义了一个名为的 JavaScript 变量myData，new Array如下所示：
var myData = new Array(['2013-01-22', 0], ['2013-01-29', 0], ['2013-02-05', 0],
['2013-02-12', 0], ['2013-02-19', 0], ['2013-02-26', 0],
['2013-03-05', 0], ['2013-03-12', 0], ['2013-03-19', 0],
['2013-03-26', 0], ['2013-04-02', 21], ['2013-04-09', 2]);
I am wondering if it is possible to sum the number values found in the array (ex. 0+0+21+2+0 and so on) and have probably a variable with the result that I can use outside of the script tag because I have 7 of this kind of arrays corresponding for each of the day in the week. I want to make a comparison afterwards based on that. That is the most preferred method for this kind of actions if is possible?
我想知道是否可以对数组中找到的数值求和（例如 0+0+21+2+0 等），并且可能有一个变量，我可以在脚本标记之外使用结果，因为我有 7 个这种数组对应于一周中的每一天。我想在此基础上进行比较。如果可能的话，这是此类操作的最首选方法吗？
采纳答案by Mark Walters
Try the following
尝试以下
var myData = [['2013-01-22', 0], ['2013-01-29', 1], ['2013-02-05', 21]];
var myTotal = 0; // Variable to hold your total
for(var i = 0, len = myData.length; i < len; i++) {
myTotal += myData[i][1]; // Iterate over your first array and then grab the second element add the values up
}
document.write(myTotal); // 22 in this instance回答by KooiInc
You could use the Array.reducemethod:
您可以使用以下Array.reduce方法：
const myData = [
['2013-01-22', 0], ['2013-01-29', 0], ['2013-02-05', 0],
['2013-02-12', 0], ['2013-02-19', 0], ['2013-02-26', 0],
['2013-03-05', 0], ['2013-03-12', 0], ['2013-03-19', 0],
['2013-03-26', 0], ['2013-04-02', 21], ['2013-04-09', 2]
];
const sum = myData
.map( v => v[1] )
.reduce( (sum, current) => sum + current, 0 );
console.log(sum);See MDN
见MDN
回答by ruhanbidart
I think the simplest way might be:
我认为最简单的方法可能是：
values.reduce(function(a, b){return a+b;})
回答by Xotic750
I would use reduce
我会使用减少
var myData = new Array(['2013-01-22', 0], ['2013-01-29', 0], ['2013-02-05', 0], ['2013-02-12', 0], ['2013-02-19', 0], ['2013-02-26', 0], ['2013-03-05', 0], ['2013-03-12', 0], ['2013-03-19', 0], ['2013-03-26', 0], ['2013-04-02', 21], ['2013-04-09', 2]);
var sum = myData.reduce(function(a, b) {
return a + b[1];
}, 0);
$("#result").text(sum);
Available on jsfiddle
回答by lee penkman
Creating a sum method would work nicely, e.g. you could add the sum function to Array
创建 sum 方法会很好地工作，例如您可以将 sum 函数添加到 Array
Array.prototype.sum = function(selector) {
if (typeof selector !== 'function') {
selector = function(item) {
return item;
}
}
var sum = 0;
for (var i = 0; i < this.length; i++) {
sum += parseFloat(selector(this[i]));
}
return sum;
};
then you could do
那么你可以做
> [1,2,3].sum()
6
and in your case
在你的情况下
> myData.sum(function(item) { return item[1]; });
23
Edit: Extending the builtins can be frowned upon because if everyone did it we would get things unexpectedly overriding each other (namespace collisions). you could add the sum function to some module and accept an array as an argument if you like.
that could mean changing the signature to myModule.sum = function(arr, selector) {then thiswould become arr
编辑：扩展内置函数可能会令人皱眉，因为如果每个人都这样做，我们会意外地相互覆盖（命名空间冲突）。如果您愿意，您可以将 sum 函数添加到某个模块并接受一个数组作为参数。这可能意味着将签名更改为myModule.sum = function(arr, selector) {thenthis将变为arr
回答by Jan Jar?ík
Or in ES6
或者在 ES6 中
values.reduce((a, b) => a + b),
values.reduce((a, b) => a + b),
example:
例子：
[1,2,3].reduce((a, b)=>a+b) // return 6
回答by btk
If you want to discard the array at the same time as summing, you could do (say, stackis the array):
如果你想在求和的同时丢弃数组，你可以这样做（比如stack是数组）：
var stack = [1,2,3],
sum = 0;
while(stack.length > 0) { sum += stack.pop() };
回答by bjhamltn
You can use the native map method for Arrays. map Method (Array) (JavaScript)
您可以对数组使用本机 map 方法。 映射方法（数组）（JavaScript）
var myData = new Array(['2013-01-22', 0], ['2013-01-29', 0], ['2013-02-05', 0],
['2013-02-12', 0], ['2013-02-19', 0], ['2013-02-26', 0],
['2013-03-05', 0], ['2013-03-12', 0], ['2013-03-19', 0],
['2013-03-26', 0], ['2013-04-02', 21], ['2013-04-09', 2]);
var a = 0;
myData.map( function(aa){ a += aa[1]; return a; });
a is your result
a 是你的结果
回答by Gismo Ranas
The javascript built-in reduce for Arrays is not a standard, but you can use underscore.js:
Arrays 的 javascript 内置 reduce 不是标准，但您可以使用 underscore.js：
var data = _.range(10);
var sum = _(data).reduce(function(memo, i) {return memo + i});
which becomes
变成
var sumMyData = _(myData).reduce(function(memo, i) {return memo + i[1]}, 0);
for your case. Have a look at this fiddlealso.
对于你的情况。也看看这个小提琴。
回答by Musa
Old way (if you don't now the length of arguments/parameters)
旧方法（如果您现在不知道参数/参数的长度）
>> function sumla1(){
result=0
for(let i=0; i<arguments.length;i++){
result+=arguments[i];
}
return result;
}
>> sumla1(45,67,88);
>> 200
ES6 (destructuring of array)
ES6（数组的解构）
>> function sumla2(...x){return x.reduce((a,b)=>a+b)}
>>
>> sumla2(5,5,6,7,8)
>>
>> 31
>>
>> var numbers = [4, 9, 16, 25];
>> sumla2(...numbers);
>> 54
