JavaScript中关于表单脚本的实用技巧

避免多次提交表单

var form = document.getElementById("myform");

form.addEventListener("submit", function(event) {    
var event = event || window.event;    
var target = event.target;    
var btn = target.elements["submit-btn"];
    btn.disabled = true;
}, false);

以上代码为表单的submit事件添加了一个事件处理程序. 事件触发后, 代码取得了提交按钮, 并将其disabled属性设置为true. 注意, 不能通过onclick事件处理程序来实现这个功能. 原因是因不同浏览器之间存在”时差”: 有的浏览器会在触发表单的submit事件之前触发click事件.

根据条件修改文本框背景颜色

var textbox = document.forms[0].elements[0];

textbox.addEventListener("focus", function(event) {    var event = event || window.event,
        target = event.target;    if (target.style.backgroundColor != "red") {
        target.style.backgroundColor = "yellow";
    }
}, false);

textbox.addEventListener("blur", function(event) {    var event = event || window.event,
        target = event.target;    if (/[^\d]/.test(target.value)) {
        target.style.backgroundColor = "red";
    } else {
        target.style.backgroundColor = "";
    }
}, false);

textbox.addEventListener("change", function(event) {    var event = event || window.event,
        target = event.target;
    console.log(123)    if (/[^\d]/.test(target.value)) {
        target.style.backgroundColor = "red";
    } else {
        target.style.backgroundColor = "";
    }
}, false)

取得选择的文本

function getSelectedText(textbox) {
    if (typeof textbox.selectionStart == "number") {        
    return textbox.value.substring(textbox.selectionStart, textbox.sectionEnd);
    } else if (document.selection) {//兼容IE
        return document.selection.createRange().text;
    }
}

选择部分文本

function selecText(textbox, startIndex, stopIndex) {    
if (textbox.setSelectionRange) {
        textbox.setSelectionRange(startIndex, stopIndex);
    } else if (textbox.createTextRange) {//兼容IE8及更早版本
        var range = textbox.createTextRange();        
        range.collapse(true);        
        range.moveStart("character", startIndex);        
        range.moveEnd("character", stopIndex - startIndex);        
        range.select();
        textbox.focus();
    }
}

测试1:

textbox.addEventListener("focus", function(event) {    var event = event || window.event,
        target = event.target;    if (target.style.backgroundColor != "red") {
        target.style.backgroundColor = "yellow";
    }
    selecText(textbox, 0, 1);
}, false);

效果:

测试2:

selecText(textbox, 0, 5);

获得剪切板信息

    getClipboardText: function(event) { //获得剪切板内容
        var clipboardData = (event.clipboardData || window.clipboardData);        
        return clipboardData.getData("text");
    }

    setClipboardText: function(event, value) { //设置剪切版内容
        if (event.clipboardData) {            
        return event.clipboardData.setData("text/plain", value);
        } else if (window.clipboardData) {            
        return window.clipboardData.setData("text", value);
        }
    }

注意: Firefox, Safari, Chrome只允许在onpaste事件处理程序中访问getData( )方法. (测试2017/9/1: 在copy事件下获取返回空字符串)

用途:
在paste事件中, 可以确定剪切板的值是否有效, 如果无效, 就可以像下面示例中那样, 取消默认的行为.

textbox.addEventListener("paste", function(event) {
    var event = event || window.event;    
    text = getClipboardText(event);    
    if (!/^\d*$/.test(text)) {        
    event.preventDefault();
    }
}, false)

自动切换焦点

效果:

//HTML
 <form method="post" id="myform">
        <input type="text" name="tel1" id="textTel1" maxlength="3">
        <input type="text" name="tel2" id="textTel2" maxlength="3">
        <input type="text" name="tel3" id="textTel3" maxlength="4">
    </form>

//Js
(function() {
    function tabForward(event) {
        var event = event || window.event;
        target = event.target;

        if (target.value.length == target.maxLength) {
            var form = target.form;

            for (var i = 0, len = form.elements.length; i < len; i++) {
                if (form.elements[i] == target) {
                    if (form.elements[i + 1]) {
                        form.elements[i + 1].focus();
                    }
                }
            }
        }
    }

    var textbox1 = document.getElementById("textTel1");
    var textbox2 = document.getElementById("textTel2");
    var textbox3 = document.getElementById("textTel3");

    textbox1.addEventListener("keyup", tabForward);
    textbox2.addEventListener("keyup", tabForward);
    textbox3.addEventListener("keyup", tabForward);})();

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