javascript - Why is iframe.contentWindow == null?

Question

I use the following code to dynamically create an iframe.

var iframe_jquery = $("<iframe>")
    .addClass("foo")
    .appendTo(container); // container is a jQuery object containing a <div> which already exists

Then, I want to access its contentWindow, but it's null:

var iframe = iframe_jquery.get(0);
if (iframe){ // iFrame exists
    console.log(iframe.contentWindow); // Prints "null"
    var doc = iframe.contentWindow.document; // NullpointerException
}

So I thought: "Maybe the iframe isn't ready yet?" So I tried:

iframe_jquery.ready(function(){
    var iframe = iframe_jquery.get(0);
    console.log(iframe.contentWindow); // Prints "null"
    var doc = iframe.contentWindow.document; // NullpointerException
});

Same result.

What's wrong?

Answer 1

I had this problem last week while playing with iFrames (building an rtf editor), and yeah it's not ready yet.

I thought if I put it in a .ready() it would work, but .ready() is when the DOM is ready, not when the iFrame has loaded its contents, so I ended up wrapping my code with jQuery .load().

So try this:

$(function () {  
    $("#myiframe").load(function () {                        
        frames["myframe"].document.body.innerHTML = htmlValue;
    });
}); 

Hope this helps