Javascript：如何使用已排序的唯一数组将对象数组转换为对象？ [英] Javascript: How convert array of objects to object with sorted unique arrays?

问题描述

拥有具有此类结构的数据：

Have data that has this kind of structure:

$input = [ { animal: 'cat', name: 'Rocky', value: 1 },
           { animal: 'cat', name: 'Spot',  value: 2 },
           { animal: 'dog', name: 'Spot',  value: 3 } ];

需要尽可能快的方法转换为此格式：

Need fastest possible method for converting to this format:

$output = { animal: [ 'cat', 'dog' ],
            name: [ 'Rocky', 'Spot' ],
            value: [ 1, 2, 3 ] };

输出的键应等于输入中每个对象中的每个键。并且输出值应该是具有已排序的唯一值的数组。我发现了一些使用嵌套循环的方法，但比我想要的慢。输入数组有30,000个元素，每个对象有8个键，我能做的最好的是Chrome中的300ms。想要降到100毫秒。有没有更快的方法使用map或reduce？

The output should have keys equal to each of the keys in each object from the input. And the output values should be arrays with the sorted unique values. I found a few ways to do it using nested loops, but slower than I would like. With 30,000 elements to the input array with 8 keys for each of the objects, the best I have been able to do is 300ms in Chrome. Would like to get down to 100ms. Is there any faster method using a map or reduce?

推荐答案

这是单向的。

$input = [ { animal: 'cat', name: 'Rocky', value: 1 },
           { animal: 'cat', name: 'Spot',  value: 2 },
           { animal: 'dog', name: 'Spot',  value: 3 } ];

$output = {animal:{},name:{},value:{}};

$input.forEach(function(v,i) { 
    $output.animal[v.animal] = 1;
    $output.name[v.name] = 1;
    $output.value[v.value] = 1;
});

$output.animal = Object.keys($output.animal);
$output.name = Object.keys($output.name);
$output.value = Object.keys($output.value);

它可以防止每次都要测试每个数组。您可以进行性能比较，看看是否有帮助。

It prevents having to test each Array every time. You can performance compare to see if it helps.

实例 http://jsfiddle.net/TJVtj/1/

如果您不想对密钥进行硬编码，可以使解决方案通用。

If you don't want to hardcode the keys, you can make the solution generic.

var keys = Object.keys($input[0]),
    $output = {};

keys.forEach(function(v) {
    $output[v] = {};
});

$input.forEach(function(v) {
    keys.forEach(function(vv) {
        $output[vv][v[vv]] = 1;
    });
});

keys.forEach(function(v) {
    $output[v] = Object.keys($output[v]);
});

实例 http://jsfiddle.net/TJVtj/2/

警告。所有值都是字符串，因为它们被提取为对象键。

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