ES5

How to get distinct values from an array of objects in JavaScript

今日有個 task 其中一個地方要在 Array of Json object 中 Distinct 一個 property const data = [ { id: 1, category: 'fruit', name: 'Apple', }, { id: 2, category: 'fruit', name: 'Banana', }, { id: 3, category: 'herb', name: 'Basil', }, { id: 4, category: 'herb', name: 'Rosemary', }, { id: 5, category: 'fruit', name: 'Dragon Fruit', }, ]; 解決方法: (ES5) var categories = data.map( // try to retrieve specific property function(item) { return item.