Javascript 使用 Jquery 从本地文件中获取 JSON 对象
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Using Jquery to get JSON objects from local file
提问by ThoughtCrhyme
I'm trying to get a list of JSON objects (products) from a local file using Jquery and store all the objects in a single array called allItems. The file is co-located in the same directory as the code, and it's called "allItems.json". Here's how I'm doing it now:
我正在尝试使用 Jquery 从本地文件中获取 JSON 对象（产品）列表，并将所有对象存储在名为 allItems 的单个数组中。该文件与代码位于同一目录中，名为“allItems.json”。这是我现在的做法：
function getAllSupportedItems(){
var allItems = new Array();
$.getJSON("allItems.json",
function(data){
$.each(data.items,
function(item){
allItems.push(item);
});
});
return allItems;
}
Based on this example: http://api.jquery.com/jQuery.getJSON/
基于这个例子：http: //api.jquery.com/jQuery.getJSON/
回答by Ates Goral
For getAllSupportedItemsto be able to return any items, the AJAX call needs to run synchronously.
为了getAllSupportedItems能够返回任何项目，AJAX 调用需要同步运行。
getJSONtranslates to the following asynchronous call:
getJSON转换为以下异步调用：
$.ajax({
url: url,
dataType: 'json',
data: data,
success: callback
});
Asynchronous is the default. You therefore need to explicitly change your request to a synchronous one:
异步是默认设置。因此，您需要明确地将您的请求更改为同步请求：
$.ajax({
url: url,
dataType: 'json',
data: data,
success: callback,
async: false
});
An alternative is to rethink the way you use getAllSupportedItemsand make it into an asynchronous utility:
另一种方法是重新考虑您的使用方式getAllSupportedItems并将其变成一个异步实用程序：
function getAllSupportedItems(callback){
$.getJSON("allItems.json",
function(data){
var allItems = [];
$.each(data.items,
function(item){
allItems.push(item);
});
callback(allItems);
// callback(data.items); should also work
});
}
Update
更新
When I initially wrote this answer, jQuery didn't have built-in Deferred support. It is a lot more concise and flexible to do something like this today:
当我最初写这个答案时，jQuery 没有内置的延迟支持。今天做这样的事情更加简洁和灵活：
function getAllSupportedItems( ) {
return $.getJSON("allItems.json").then(function (data) {
return data.items;
});
}
// Usage:
getAllSupportedItems().done(function (items) {
// you have your items here
});
回答by Pointy
How are you using this? If you're expecting the main function ("getAllSupportedItems") to returnthe array you make, well that won't work. The $.getJSONfunction is asynchronous, and so the handler won't actually build the array until after the outer function has returned.
你怎么用这个？如果您希望主函数 ("getAllSupportedItems")返回您创建的数组，那么这将不起作用。该$.getJSON函数是异步的，因此在外部函数返回之前，处理程序实际上不会构建数组。
