Set iframe innerHTML without loading page in it (with jquery)

If you want to avoid using document.write, which is generally not recommended any longer, you can get at the frame contents to add the content:

iframe = $('<iframe id="thepage"></iframe>')
iframeHtml = 'iframeHtml'
$('body').append(iframe)
iframe.contents().find('body').html(iframeHtml)

the best way to populate frame contents is document.write

var dstFrame = document.getElementById('yourFrameId');
var dstDoc = dstFrame.contentDocument || dstFrame.contentWindow.document;
dstDoc.write(yourHTML);
dstDoc.close()

UPD: that is

var iFrame = $('<iframe id="thepage"></iframe>');
$('body').append(iFrame);

var iFrameDoc = iFrame[0].contentDocument || iFrame[0].contentWindow.document;
iFrameDoc.write('<p>Some useful html</p>');
iFrameDoc.close();