four approachs can cross domain in javascript
1.jsonp
2.document.domain(only in frame and they have one same parent domain)
3.window.name
4.window.postMessage(only in Html5)
original website:http://www.cnblogs.com/2050/p/3191744.html
[cross domain] four approachs to cross domain in javascript
原文：http://www.cnblogs.com/langu/p/3950861.html