window.crypto.getRandomValues(new Uint32Array(1))[0];
浏览器支持情况如下：
IE: no IE Mobile: no Firefox24+ Firefox Mobile: will be in 21 Safari: from 3.1 Safari Mobile: from iOS 6 Chrome: from 11 Chrome for Mobile: from 23 Android browser (before 4.0 as replaced with Chrome): no Opera: no (though will probably get it when moving to WebKit) Opera Mobile: no Opera Mini: no