Why IE doesn't accept brackets when we call a function

I don't know why I have an function like:

<script type="text/javascript">
    func开发者_Go百科tion setSomeEnvValue() {
        myLoadStatus = true;
        myColor = 'black';
    }
    window.onload = setSomeEnvValue();
</script>

I don't know why IE show error at:

window.onload = setSomeEnvValue();

When I change this code to:

window.onload = setSomeEnvValue;

It makes me crazy. If setSomeEnvValue() has some arguments like setSomeEnvValue(myVar1, myVar2), how can I call it when using it in IE?

Thanks you very much!

In this case, IE has the correct implementation.

When you set a callback (or event handler), such as window.onload, you're basically telling the browser that the function that you're giving it should be executed when that event is triggered.

By writing window.onload = setSomeEnvValue();, you're saying that the return value of setSomeEnvValue should be called whenever the window.onload event is triggered. Of course, this may be possible if your function returns a closure, but I'm going to assume that's not the case here.

What window.onload = setSomeEnvValue(); means is to run setSomeEnvValue() now and assign its result to window.onload. What you need is to assign the function itself to window.onload, so that the browser can run it later.

If you want window.onload to call a function with some arguments that you know in advance, make a new function (with no arguments) that calls the other function with the desired arguments, and assign that to window.onload.

function myOnload() {
  setSomeEnvValue(myVar1, myVar2);
}

window.onload = myOnload;

or even

window.onload = function() { setSomeEnvValue(myVar1, myVar2); }