JSFiddle - React, Tailwind, and code Playground
JavaScript
var $iframe1 = $('<iframe allowtransparency="true" src="http://google.com"/>').appendTo('body');
var $iframe2 = $('<iframe />').attr({
allowtransparency: true,
src: "http://google.com"
}).appendTo('body');
console.log($iframe1.attr('allowtransparency'));
console.log($iframe2.attr('allowtransparency'));