使用javascript将div插入dom中？

Question

im trying to insert a new div into the DOM with an id of "app"

var new_div = document.createElement("div");
var app_div = document.getElementById("app");
document.body.insertBefore(new_div, app_div);​

this gives me an error in the console:

Uncaught TypeError: Cannot call method 'insertBefore' of null

but i don't know why?

Answer 1

You need to wrap your code to window.onload handler:

window.onload = function() {
    var new_div = document.createElement("div");
    var app_div = document.getElementById("app");
    document.body.insertBefore(new_div, app_div);
}

---

Example on jsFiddle .

Answer 2

除了按照Igor的建议将其更好地包装在onload（）之外，您是否不想先将new_div添加到文档中？

document.body.insertBefore(new_div, document.body.firstChild);

Answer 3

尝试使用jquery document.ready事件