如何使用 JavaScript 對包含父對象和子對象的數組進行排序？

Question

我有一個包含 object 的數組，我需要對它進行排序，首先應該出現父 object，然后是其子對象，依此類推。 但是，當我嘗試在數組中查找父 object 的索引以便將子 object 推到它之后時，findIndex() 方法返回 -1。 有人可以指出這個問題的根源，因為我無法清楚地看到它為什么會這樣做。 我正在使用的代碼和數據數組寫在下面。

 const data = [ { "_id": "0", "parent": null, "title": "All" }, { "_id": "61c0a9cb8f67e811d55abb2d", "parent": null, "title": "Electronics" }, { "_id": "61c0a9cb8f67e811d55abb2e", "parent": { "_id": "61c0a9cb8f67e811d55abb2d" }, "title": "Phones" }, { "_id": "61c0a9cb8f67e811d55abb2f", "parent": { "_id": "61c0a9cb8f67e811d55abb2d" }, "title": "Laptops" }, { "_id": "61c0a9cb8f67e811d55abb30", "parent": { "_id": "61c0a9cb8f67e811d55abb2d" }, "title": "TVs" }, { "_id": "61c0a9cb8f67e811d55abb31", "parent": null, "title": "Literature" }, { "_id": "61c0a9cb8f67e811d55abb32", "parent": { "_id": "61c0a9cb8f67e811d55abb31" }, "title": "Study Literature" }, { "_id": "61c0a9cb8f67e811d55abb33", "parent": { "_id": "61c0a9cb8f67e811d55abb31" }, "title": "Fictional Literature" }, { "_id": "61c0a9cb8f67e811d55abb34", "parent": { "_id": "61c0a9cb8f67e811d55abb31" }, "title": "Comic books" }, { "_id": "61c0a9cb8f67e811d55abb35", "parent": { "_id": "61c0a9cb8f67e811d55abb2e" }, "title": "Smartphones" }, { "_id": "61c0a9cb8f67e811d55abb36", "parent": { "_id": "61c0a9cb8f67e811d55abb35" }, "title": "Accessories" } ]; let parents= []; data.forEach(element => { if(element.parent == null ) { parents.push(element); } else { let parentId = element.parent._id; let index = parents.findIndex(item => { return item._id == parentId; }); parents.splice(index+1, 0, element); }; });

Answer 1

使用item => {parentId == item._id;}確實需要使用“return”： item => {return parentId == item._id;}沒有返回功能基本上是item => null ； .findIndex()將其視為錯誤，導致 -1

如果您使用沒有大括號的箭頭 function 則暗示返回（但將您限制為單行表達式作為權衡）： item => parentId == item._id

來源： https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions