从 JSON 数组键值对动态检索键 - Javascript [英] Retrieving Keys from JSON Array key-value pair dynamically - Javascript

问题描述

我有一个问题想请教您的专业知识.

I have a question that would like to seek your expertise on.

这是我拥有的 JSON 数组:

This is a JSON array that I have:

[{"A":20,"B":32,"C":27,"D":30,"E":40}]

我想做的是从 JSON 数组中检索键(A、B、C、D、E)而不是值.我能够检索值但不能检索键.

What I would like to do is to retrieve the keys (A, B, C, D, E) from the JSON array instead of the values. I am able to retrieve the values but not the keys.

我正在使用它来动态检索值:

I am using this to retrieve the values dynamically:

function calculateSum(jsonArray) {
    var result = 0;
    for (var i = jsonArray.length - 1;  i >= 0; --i)
    {
        var o = jsonArray[i];
        A = o.A;
        B = o.B;
        C = o.C;
        D = o.D;
        E = o.E;
        result = A + B + C + D + E;
        return result;
    }

    return result;
}

同样，我应该怎么做才能使用 JavaScript 检索键?

Similarly, what should I do to retrieve the keys using JavaScript?

推荐答案

你在使用 D3.js正如您的标签所暗示的那样?因为在那种情况下，你可以只使用 d3.keys():

Are you using D3.js as your tag implies? Because in that case, you can just use d3.keys():

var data = [{"A":20,"B":32,"C":27,"D":30,"E":40}];
d3.keys(data[0]); // ["A", "B", "C", "D", "E"] 

如果您想要所有值的总和，最好使用 d3.values() 和 d3.sum():

If you want the sum of all the values, you might be better off using d3.values() and d3.sum():

var data = [{"A":20,"B":32,"C":27,"D":30,"E":40}, {"F":50}];
// get total of all object totals
var total = d3.sum(data, function(d) {
    // get total of a single object's values
    return d3.sum(d3.values(d));
});
total; // 199

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