Json数据转换为javascript数组(Json data into javascript array)

var test=[];
$(document).ready(function(){
            $.getJSON("data.json",function(data){
                $.each(data,function(key,value){
                    test.push(value.topic);
                });
            });
        });
 
 这是我的javacript代码。 我想用键作为主题推送json对象的所有值。 但是当我尝试访问test [i]（我是数组长度内的任何整数）时，出现“undefined”错误。 我有什么困难？ 
 
 这是我的json对象sample- 
 
[
        {
            "topic": "Books",
            "quantity": 3
        },
        {
            "topic": "Grossery",
            "quantity": 3
        },
        {
            "topic": "stationery",
            "quantity": 3
        },
        {
            "topic": "food",
            "quantity": 2
        },
        {
            "topic": "market items",
            "quantity": 3
        }
]

var test=[];
$(document).ready(function(){
            $.getJSON("data.json",function(data){
                $.each(data,function(key,value){
                    test.push(value.topic);
                });
            });
        });
 
Here is my javacript code. I want to push json object's all values with key as topic. But when I try to access test[i] (i be any integer within array length) I get an error "undefined" . What' am I msissing?
 
Here is my json object sample-
 
[
        {
            "topic": "Books",
            "quantity": 3
        },
        {
            "topic": "Grossery",
            "quantity": 3
        },
        {
            "topic": "stationery",
            "quantity": 3
        },
        {
            "topic": "food",
            "quantity": 2
        },
        {
            "topic": "market items",
            "quantity": 3
        }
]

原文：https://stackoverflow.com/questions/50134338