Init polymer attributes before ready()

问题

When dynamically creating polymer elements in js, how to initialize attributes before ready() event? my code below:

var el = document.createElement("my-elem");
el.setAttribute("myAttr", 123); // or el.myAttr = 123.

the ready() event is fired before myAttr is set. actually I want it works like it does in HTML way:

var div = document.createElement("DIV");
div.innerHTML('<my-elem myAttr="123"></my-elem>');
var el = div.children[0];

in this way, myAttr is set when ready() event working, but the code is kinda ugly. is there a way like this:

var el = document.createElement("my-elem", { myAttr: 123});

来源：https://stackoverflow.com/questions/27543950/init-polymer-attributes-before-ready