201508061040_《移动开发之——解决header定位差异问题代码》

function isSupportFixed() {
var userAgent = window.navigator.userAgent,
ios = userAgent.match(/(iPad|iPhone|iPod)\s+OS\s([\d_\.]+)/),
ios5below = ios && ios[2] && (parseInt(ios[2].replace(/_/g, '.'), 10) < 5),
operaMini = /Opera Mini/i.test(userAgent),
body = document.body,
div, isFixed;

div = document.createElement('div');
div.style.cssText = 'display:none;position:fixed;z-index:100;';
body.appendChild(div);
isFixed = window.getComputedStyle(div).position != 'fixed';
body.removeChild(div);
div = null;

return !!(isFixed || ios5below || operaMini);
}