Windows onload无法从外部脚本触发

Question

Okay i know this has been asked a lot but it seems that none of the solutions actually work for me. Here's the situation. I have a webpage that i need to add to an existing site, this site uses a master page which i can not touch. This limits me to using javascripts window.onload because i do not have access to the body tag.

On my page i have linked my external .js file in the head beneath every other external file. Here is an example of what my .js file looks like.

var myobj = null;
(5 or so functions that work properly. Mainly just toggles that show and hide divs. none touch the onload)
function load(){
myobj = document.getElementById("my_element");
alert("test");
}
window.onload = load;

Tried this and the load function never fires as i never get the alert. I've tried commenting out the first line in the load function and only haven't the alert and still nothing. Looking around i also found another way to do it that i tried without success. Everything else is the same except i removed the window.load and added this.

function addLoadEvent(func) {
var oldonload = window.onload;
if (typeof window.onload != 'function') {
    window.onload = func;
} else {
    window.onload = function () {
        if (oldonload) {
            oldonload();
        }
        func();
    }


  }
}
addLoadEvent(load);
addLoadEvent(function () {
    /* more code to run on page load */
    alert("hello2");
});

In this function, neither of the alerts fire. I have also tried placing an alert outside of a function, that one does work.

The browsers i am using are IE 8.0.7600.16385 and Chrome 21.0.1180.60

Let me know if you need more information.

Oh and as a side note, i cannot use jquery or any other javascript library as we are trying to keep this as light as possible. This page also must work in IE8, that is the businesses only supported browser at the moment. It would be nice if it worked in Chrome as well.

EDIT In case i'm going about this completely the wrong way, what i am trying to do is keep track of the last element i have. I essentially have a page with 2 columns, left side is a menu and right is content. The content is all placed in div's with only one category showing at a time. The way it is supposed to work is when clicking on the menu category it hides the previous content and shows the new content.

I have set my content class to display: none; and have the start_content ID set to display: block;. What the Javascript is supposed to do is initialize my global with the start_content object. When clicking in the menu it calls a function that does an obj.style.display = 'none' and then sets the new obj to display = 'block'. It then takes the new obj and places it in my global variable to be changed on the next menu click.

here's an example without any of the onload functions

var prevContent = document.getElementById("start_content");
function toggle(id) {
prevContent.style.display = "none";
var content = document.getElementById(id);
content.style.display = "block";
prevContent = content;
}

The problem with this is that prevContent is unidentified when it enters the toggle function. I had assumed this was because i am linking this .js file in the head and so the page hasn't loaded my start_content yet which is why i had changed it to declaring the global as a null and then setting up a window.onload to set the appropriate value after it is created.

Answer 1

最后，将“ Defer”添加到脚本标签中就可以了。