Dynamically insert a frame inside a frameset as first frame in native javascript?

var m = document.getElementById('mainframeset');
m.appendChild(newFrame);

inserts a frame inside a frameset as last frame.

What I want here is to insert the frame as the first frame.

Something like this :

frameSet[0].insertBefore(newframe, frameSet[0].document.frames[0]);

开发者_开发问答

It doesn't work,though.

Thaks

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frameSet[0].insertBefore(newframe, frameSet[0].firstChild);