javascript在嵌套数组中查找子对象 [英] javascript find child object in nested arrays

问题描述

我具有如下所示的javascript结构(嵌套的对象数组)

var categoryGroups = [
    {
        Id: 1, Categories: [
            { Id: 1 },
            { Id: 2 }, 
        ]

    },
    {
        Id: 2, Categories: [
            { Id: 100 },
            { Id: 200 },
        ]

    }
]

假设类别ID都是唯一的，我想找到一个与ID匹配的子类别对象.

我在下面有此内容，但想知道是否还有更简洁的方法:

var category, categoryGroup, found = false;
for (i = 0; i < categoryGroups.length ; i++) {
    categoryGroup = categoryGroups[i];
    for (j = 0; j < categoryGroup.Categories.length; j++) {
        category = categoryGroup.Categories[j];
        if (category.Id === id) {
            found = true;
            break;
        }
    }
    if (found) break;
}

解决方案

注意事项:这使用了几个Array.prototype函数，这些函数仅在ECMAScript 5中添加，因此无法使用使用旧版浏览器，除非您对其进行填充.

您可以遍历数组中的所有第一级对象，然后根据您的条件过滤类别并收集数组中的所有匹配项.您的最终结果将是匹配数组中的第一个元素(如果数组为空，则找不到匹配项).

var matches = [];
var needle = 100; // what to look for

arr.forEach(function(e) {
    matches = matches.concat(e.Categories.filter(function(c) {
        return (c.Id === needle);
    }));
});

console.log(matches[0] || "Not found");

JSFiddle:: http://jsfiddle.net/b7ktf/1/

参考:

Array.prototype.forEach
Array.prototype.concat
Array.prototype.filter

I have a javascript structure like below (nested arrays of objects)

var categoryGroups = [
    {
        Id: 1, Categories: [
            { Id: 1 },
            { Id: 2 }, 
        ]

    },
    {
        Id: 2, Categories: [
            { Id: 100 },
            { Id: 200 },
        ]

    }
]

I want to find a child Category object matching an Id, assuming the Category Id's are all unique.

I've got this below, but was wondering if there is a more concise way of doing it:

var category, categoryGroup, found = false;
for (i = 0; i < categoryGroups.length ; i++) {
    categoryGroup = categoryGroups[i];
    for (j = 0; j < categoryGroup.Categories.length; j++) {
        category = categoryGroup.Categories[j];
        if (category.Id === id) {
            found = true;
            break;
        }
    }
    if (found) break;
}

解决方案

Caveat: This uses a couple of Array.prototype functions that were only added in ECMAScript 5 and thus will not work with older browsers unless you polyfill them.

You can loop over all first-level objects in your array, and then filter the categories based on your condition and collect all matches in an array. Your final result will be the first element in the array of matches (no match found if array is empty).

var matches = [];
var needle = 100; // what to look for

arr.forEach(function(e) {
    matches = matches.concat(e.Categories.filter(function(c) {
        return (c.Id === needle);
    }));
});

console.log(matches[0] || "Not found");

JSFiddle: http://jsfiddle.net/b7ktf/1/

References:

Array.prototype.forEach
Array.prototype.concat
Array.prototype.filter

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