Javascript初学者 - 全局变量不起作用

I want to give out the value (defined in function getInfo) of the global var "title" but all i get at the alert(title) is "undefined". Sure i can put the alert in the last function but why i doesnt work this way?

我想给出全局变量“title”的值(在函数getInfo中定义),但是我得到的警报(标题)是“未定义”。当然,我可以把警报放在最后一个功能,但为什么我不这样做?

//[...]
var title;//global var

$(document).ready(
function(){                    
    $.getJSON(url, displayImages)//open func displayImages
});

function displayImages(data) {                                                                                                                                              
    $.each(data.photoset.photo, function(i,item){
            $.getJSON(url+item.id+"&format=json&jsoncallback=?", getInfo);//open func getInfo
            alert(title);//output: undefined

    });     

}

function getInfo(data2){
    title = data2.photo.title._content;//get value of title from json

}

1 个解决方案

#1

$.getJSON is asynchronous, which means that if you put an alert in the getInfo method, it would fire after the alert(title) even though it is a line before it.

$ .getJSON是异步的,这意味着如果你在getInfo方法中放置一个警报,它将在警报(标题)之后触发,即使它是它之前的一行。

You could fix this as such:

你可以解决这个问题:

$.getJSON(url+item.id+"&format=json&jsoncallback=?", function(data) { 
  getInfo(data);
  alert(title);
});

#1