viewport をjsで管理 タブレットをPC表示にしたい

<script type="text/javascript">
if ((navigator.userAgent.indexOf('iPhone') > 0) || navigator.userAgent.indexOf('iPod') > 0 || navigator.userAgent.indexOf('Android') > 0) {
	    document.write('<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">');
	}else{
	    document.write('<meta name="1200" content="width=device-width, initial-scale=1,minimum-scale=1, maximum-scale=1, user-scalable=yes">');
	}
</script>