JS验证文本框字数并做限制和提示

旧城等待， 2022-04-10 12:49 302阅读 0赞

### **效果如图；解决输入时拼音长度也算字符串长度的问题。** ###

![20190107124255612.png][]

![20190107124322743.png][]

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <meta http-equiv="X-UA-Compatible" content="ie=edge">
        <title>Document</title>
    </head>
    <body>
        还可以输入<span id="word">10</span>个字<br />
        <textarea id="txt" maxlength="10"></textarea>
    </body>
    </html>
    <script language="javascript" type="text/javascript">
        var txt = document.getElementById("txt");
        var txtNum = document.getElementById("word");
        var maxlength = 10;
        var sw = false; //定义关闭的开关
        txt.addEventListener("keyup", function () {
            if (sw == false) {
                countTxt();
            }
        });
        //ompositionstart在输入中文或者语音等需要等待一连串的输入的操作之前触发
        txt.addEventListener("compositionstart", function () {
            sw = true;
        });
        //compositionend在输入中文或者语音等完毕或取消时触发
        txt.addEventListener("compositionend", function () {
            sw = false;
            countTxt();
        });
        //这两个属性有点类似于“开关”，如：开始输入拼音时开关打开，不再改变监测得到的长度数值。用拼音完整输入一个或是一串文字后，开关关闭，此时得到监测的数值长度。
        function countTxt() { //计数函数
            if (sw == false) { //只有开关关闭时，才赋值
                txtNum.textContent = maxlength - txt.value.length;
            }
        }
    </script>

[20190107124255612.png]: /images/20220330/d376c67ed12c43d390d1e48a5bfff1c2.png
[20190107124322743.png]: /images/20220330/b09c00d5a8084d9b8e6d5e3d2039132b.png