How can I check whether a button (wpv_1266351) in a frame does or does not exist using Jquery or Javascript?

iframe Info: id="AssessmentsIFrame"

button Info: id="wpv_1266351"开发者_StackOverflow

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$('#AssessmentsIFrame').contents().find('#wpv_1266351');

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First, the iframe HAS to be on the same domain name, otherwise you can't get to anything in it.

var ifr = $('#'),
 ifrDoc = ifr.contentDocument || (ifr.contentWindow && ifr.contentWindow.document) || ifr.document,
 button = ifrDoc.getElementById('wpv_1266351');

button will either be null or a reference to your button. It's not really any simpler using jQUery since jQuery doesn't know how to get the iframe document reference by itself.