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  • js控制还能输入多少个字符

    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>还可以输入多少个字符</title>
    <script type="text/javascript">
        window.onload = function() {
            var oTta = document.getElementById("tta"),
                oAllNumInp = document.getElementById("all-num-inp"),
                oNeedNumInp = document.getElementById("need-num-inp"),
                oHasNumInp = document.getElementById("has-num-inp");
            
            var maxNum = 20;
            
            var oTtaVal = "";
            
            oTta.onkeyup = function() {
                checkFont();
            };
            
            oTta.onkeydown = function() {
                checkFont();
            };
            
            function checkFont() {
                oTtaVal = oTta.value;
                if(oTtaVal.length > maxNum) {
                    oTta.value = oTtaVal.substring(0, maxNum);
                    oNeedNumInp.value = 0;
                    oHasNumInp = maxNum;    
                } else {
                    oNeedNumInp.value = maxNum - oTtaVal.length;
                    oHasNumInp.value = oTtaVal.length;    
                }    
            }
            
        };
    </script>
    </head>
    
    <body>
        <textarea id="tta" cols="40" rows="10"></textarea>
        <div>
            <p id="all-num">一共有多少个字符:</p><input id="all-num-inp" type="text" />
        </div>
        <div>
            <p id="need-num">还可以输入</p><input id="need-num-inp" type="text" />
        </div>
        <div>
            <p id="has-num">已输入:</p><input id="has-num-inp" type="text" />
        </div>
    </body>
    </html>

    还有一种判断的方式是:

    它允许你一直输入,但是超过的时候会提示你已超出多少多少,这个思路也不错

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  • 原文地址:https://www.cnblogs.com/king-bj/p/4487956.html
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