onload Functions Firing Out Of Order_问答_开发者

开发者 https://www.devze.com 2023-02-10 06:52 出处：网络

Any idea why the following code: <script> var access_token; var access_token_secret; function Login(){

Any idea why the following code:

    <script>        
        var access_token;
        var access_token_secret;        

        function Login(){
            img = document.getElementById('authenticate');
            img.src = 'authenticate.png';
            login = document.getElementById('login');
            login.style.visibility="visible";
        }
        function cookieHandlerStep1(){
            chrome.cookies.get({ 
                url:URL_GOES_HERE, 
                name:'access_token'
            },
            function(cookie){
                if(cookie){ 
                    access_token = cookie['value'];
                    cookieHandlerStep2();
                } else{ 
                    Login();
                }
            });
        }
        function cookieHandlerStep2(){
            chrome.cookies.get({ 
                url:URL_GOES_HERE, 
                name:'access_token_secret'
            },
            function(cookie){
                if(cookie){ 
                    access_token_secret = cookie['value'];
                    Interact();
                } else{ 
                    Login();
                }
            });
        }
        function Interact(){
            alert(access_token);
            xhr = new XMLHttpRequest();
            xhr.open("GET", URL_GOES_HERE, true);
            xhr.onreadystatechange = function() {
              if (xhr.readyState == 4) {
                    document.write(xhr.responseText);
              }
            }
            xhr.send();
        }
    </script>


<body onload="cookieHandlerStep1(),cookieHandlerStep2(),Interact()">

Could possibly have the functions executing out of s开发者_JAVA百科equence?

They're not firing out of order. You've provided callbacks to chrome.cookies.get which are not guaranteed to be called before the rest of the code. The first function returns before the callbacks are fired, and the next two (cookieHandlerStep2() and Interact()) get called.

However, in these callbacks, cookieHandlerStep1() is already calling cookieHandlerStep2() which then calls Interact() - so I presume what you actually want in your onload is just the first function to initiate the chain: