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textarea高度隨文字增多變化高度

<!DOCTYPE html>
<html>
<head>
<title>autoresizing textarea</title>
<script src="js/jquery.min.js"></script>
<style type="text/css">
textarea {
    border: 1px solid red;
    overflow: hidden;
    padding: 0;
min-height:100px;
max-height:300px;
}
</style>
</head>
<body onload="init();">
<textarea rows="5" style="height:25px;" id="text"></textarea>


<script type="text/javascript">
var observe;
if (window.attachEvent) {
    observe = function (element, event, handler) {
        element.attachEvent('on'+event, handler);
    };
}
else {
    observe = function (element, event, handler) {
        element.addEventListener(event, handler, false);
    };
}
function init () {
    var text = document.getElementById('text');
    function resize () {
        text.style.height = 'auto';
        text.style.height = text.scrollHeight+'px';
    }
    /* 0-timeout to get the already changed text */
    function delayedResize () {
        window.setTimeout(resize, 0);
    }
    observe(text, 'change',  resize);
    observe(text, 'cut',     delayedResize);
    observe(text, 'paste',   delayedResize);
    observe(text, 'drop',    delayedResize);
    observe(text, 'keydown', delayedResize);
    text.focus();
    text.select();
    resize();
}
</script>
</body>
</html>