Lodash 从重复的对象键创建集合

Question

我有以下结构：

var output = [{
    "article": "BlahBlah",
    "title": "Another blah"
}, {
    "article": "BlahBlah",
    "title": "Return of the blah"
}, {
    "article": "BlahBlah2",
    "title": "The blah strikes back"
}, {
    "article": "BlahBlah2",
    "title": "The blahfather"
}]

从上面使用优雅的 lodash 单线，我需要创建以下结构。

var newOutput = [{
    "article": "BlahBlah",
    "titles": ["Another blah", "Return of the blah"]
}, {
   "article": "BlahBlah2",
   "titles": ["The blah strikes back", "The blahfather"]
}]

非常感谢您一如既往的帮助。解释解决方案的工作原理是一个巨大的优势。

Answer 1

使用_.groupBy，然后使用_.map 生成的对象到对象数组。

var newOutput = _(output)
    .groupBy('article')
    .map(function(v, k){ return { article: k, titles: _.map(v, 'title') } })
    .value();

var output = [{"article":"BlahBlah","title":"Another blah"},{"article":"BlahBlah","title":"Return of the blah"},{"article":"BlahBlah2","title":"The blah strikes back"},{"article":"BlahBlah2","title":"The blahfather"}];

let newOutput = _(output)
    .groupBy('article')
    .map(function(v, k){ return { article: k, titles: _.map(v, 'title') } })
    .value();

console.log(newOutput);

<script src="https://cdn.jsdelivr.net/lodash/4.13.1/lodash.min.js"></script>

使用 ES6 箭头函数，

var newOutput = _(output)
    .groupBy('article')
    .map((v, k) => ({ article: k, titles: _.map(v, 'title') }))
    .value();

Answer 2

更好的 lodash 版本可能是（使用很棒的 chaining 方法）

_(a).groupBy('article').map( (x,k) => ({ article: k, titles:_.map(x, 'title')}) ).value();  

如果你想按文章分组（所以文章是关键，有助于快速查找）

_(a).groupBy('article').mapValues(x => _.map(x, 'title')).value();

Answer 3

纯 Javascript 的提案

它使用 IIFE（立即调用函数表达式）来使用私有变量并在数组中收集返回值。

此外，它使用哈希表来引用正确的数组项。

var output = [{ article: "BlahBlah", title: "Another blah" }, { article: "BlahBlah", title: "Return of the blah" }, { article: "BlahBlah2", title: "The blah strikes back" }, { article: "BlahBlah2", title: "The blahfather" }],
    newOutput = function (data) {
        var r = [];
        data.forEach(function (a) {
            if (!this[a.article]) {
                this[a.article] = { article: a.article, titles: [] };
                r.push(this[a.article]);
            }
            this[a.article].titles.push(a.title);
        }, Object.create(null));
        return r;
    }(output);
        
console.log(newOutput);