手机端自适应缩放显示 js

<script>var _width = parseInt(window.screen.width);var scale = _width/640;var ua = navigator.userAgent.toLowerCase();var result = /android (/d+/./d+)/.exec(ua);if (result){var version = parseFloat(result[1]);if(version>2.3){document.write('<meta name="viewport" content="width=640, minimum-scale = '+scale+', maximum-scale = '+scale+', target-densitydpi=device-dpi">');}else{document.write('<meta name="viewport" content="width=640, target-densitydpi=device-dpi">');}} else {document.write('<meta name="viewport" content="width=640, user-scalable=no, target-densitydpi=device-dpi">');}</script>

注：参考于网上代码，笔记记下