https://www.wakeoe.com/shared/js/viewport.js

1var baseW = 767;	//break poiint setting add viewport 
2var iOSviewportW = 0;
3//var viewport = 1200 // width viewport;
4var ua = navigator.userAgent.toLowerCase();
5var isiOS = (ua.indexOf("iphone") > -1) || (ua.indexOf("ipod") > -1) || (ua.indexOf("ipad") > -1);
6if(isiOS){
7	iOSviewportW = document.documentElement.clientWidth;
8}
9function updateMetaViewport(){
10	var viewportContent;
11	var w = window.outerWidth;
12	//if(isiOS){
13	//	w = iOSviewportW;
14	//}
15	if(w > baseW){
16		viewportContent = "width=1200,user-scalable=no,shrink-to-fit=no";
17	}else{
18		viewportContent = "width=device-width, shrink-to-fit=no";
19	}
20	document.querySelector("meta[name='viewport']").setAttribute("content", viewportContent);
21}
22
23window.addEventListener("resize", updateMetaViewport, false);
24window.addEventListener("orientationchange", updateMetaViewport, false);
25
26var ev = document.createEvent("UIEvent");
27ev.initEvent("resize", true, true)
28window.dispatchEvent(ev);