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);})();