javascript - All js files introduced by the page, each js file has window.onload. Occasionally, a certain js file is not executed.

Question

1. Introduce a.js and b.js in page A; there is no problem with both a.js and b.js using window.onload;
But I also introduce a.js and c in page B. js, occasionally a.js is as if it is not executed at all
But I directly put the things in window.onload in a.js into the onload of c.js in page B, and it is executed correctly. I don’t know why. what happened? ?

Answer 1

window.onload is only used once, so there will be conflicts when multiple js use it at the same time.
Solution

1.用jQuery使用ready()方法替换onload
2.在window.onload中一次加载所有js文件，例：window.onload=function(){function(a);function(b);} 

Answer 2

I tried it. The window can be bound multiple times, but it will only take effect the last time. You can compare my two examples below to understand your situation.

    //方式1:
    window.onload=function () {
        console.log("1");
    }
    window.onload=function () {
        console.log("2");
    }
//    输出2
//    -------------------------------分割线
//    方式2:
    function fn1() {
        console.log("1");
    }
    function fn2() {
        console.log("2");
    }
    addEventLoad(fn1);
    addEventLoad(fn2);
    //输出1  2
    function addEventLoad(fn){
        var oldFn = window.onload;
        if(typeof window.onload != 'function'){
            window.onload = fn;
        }else{
            window.onload = function(){
                oldFn();
                fn();
            }
        }
    }

Answer 3

• For events set through the window.onload = function() { ... } method, the later window.onload value will overwrite the previous one, so only the last one will take effect. (This is the same as calling a = 1; a = 2; a =3; )

• If you need to bind the onload event of window multiple times, it is recommended to use addEventListener:

window.addEventListener('load', function() { ... }, false);

• Note that attachEvent is used in the ID instead of addEventListener:

window.attachEvent('onload', function() { ... });

• Also note that 'load' is used in addEventListener, while 'onload' is used in attachEvent.

Answer 4

The window.onload() method can only be bound once. If you bind multiple times, only the last one will take effect

Answer 5

window.onload will only call the last one, and the previous ones will be overwritten.