em 和 px相互转换

时间：2021-08-08 19:59:35
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
        function convert (id) {
            var px_val = document.getElementById('pxToEm').value,
                em_val = document.getElementById('emToPX').value,
                base_val = document.getElementById('basePX').value;
            if(!base_val){
                document.getElementById('tip').value = '基本单位不能为空';
                return;
            }else{
                document.getElementById('tip').value = '';
            }
            base_val = base_val.replace(/[^0-9.]/g, '');
            if(id === 'PXtoEMConvert'){
                if(!px_val){
                    document.getElementById('tip').value = 'PX to EM不能为空';
                    return;
                }
                px_val = px_val.replace(/[^0-9.]/g, '');
                document.getElementById('tip').value = '';
                document.getElementById('result').value=((px_val / base_val).toFixed(3) + 'em');
            }else if(id === 'EMtoPXConvert'){
                if(!em_val){
                    document.getElementById('tip').value = 'EM to PX不能为空';
                    return ;
                }
                em_val = em_val.replace(/[^0-9.]/g, '');
                document.getElementById('tip').value = '';
                document.getElementById('result').value=(parseInt(em_val * base_val) + 'px');
            }
        }
    </script>
</head>
<body>
    <img src="px_em.png" alt="px和em单位相互转换">
    <br>
    <label for="basePx">基本单位:</label>
    <input type="number" id="basePX">px
    <br>
    <label for="pxToEm">PX to EM:</label>
    <input type="number" id="pxToEm">px
    <br>
    <label for="emToPX">EM to PX:</label>
    <input type="number" id="emToPX">em
    <br>
    <label for="result">转换结果:</label>
    <input type="text" id="result">
    <br>
    <input type="button" id="PXtoEMConvert" onclick="convert(this.id)" value="PX to EM转换">
    <input type="button" id="EMtoPXConvert" onclick="convert(this.id)" value="EM to PX转换">
    <br>
    <label for="tip">提示:</label>
    <input type="text" id="tip" readonly>
</body>
</html>
相关文章链接：
http://www.cnblogs.com/leejersey/p/3662612.html

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