Last week, I shared how to check if an input is empty with CSS. Today, let’s talk about the same thing, but with JavaScript. It’s much simpler. Here’s what we’re building: Events to validate the input If you want to validate the input when a user types into the field, you ...
letinputValue=document.getElementById('inputId').value;// 通过id获取输入框的值 1. 这里的inputId是你在HTML中定义输入框的id值。 步骤2:判断输入框的值是否为空 接下来,我们需要判断输入框的值是否为空。可以通过以下代码来实现: if(inputValue===''){// 输入框的值为空,执行相应操作}else{// 输入...
isEnd = function () { return this.end; } } function Trie() { this.root = new Node(); this.add = function (input, node = this.root) { if (input.length === 0) { node.setEnd(); return; } else if (!node.keys.has(input[0])) { node.keys.set(input[0], new Node()); ...
需求逻辑： H5 code <input type='file' id="file"> 我想判断input文件对象的文件是否为空，惨了！
if ( xArr != null ) { for(i=0;i<xArr.length;i++) { writeToLog(xArr[i]); } } else { writeToLog("no match"); } 最终控制台输出: 2019/08/19 13:21:19 - JavaScript代码.0 - info 2019/08/19 13:21:19 - JavaScript代码.0 - proconis ...
()" > 姓名:<input type="text" id="uname" /> <input type="submit" value="提交表单" onclick="return submitForm()" /> </form> </body> <script> function submitForm() { var uname = document.getElementById("uname").value; if (uname == null || uname.trim() == "") { return...
functionPriorityQueue() {...this.enqueue =function(element) {if (this.isEmpty()) {collection.push(element);}else{var added =false;for(var i = 0; i < collection.length; i++) {if (element[1] < collection[i][1]) {collection.splice(i, 0, element);added =true;break;}}if (!added...
functionvalidateForm() {// 验证用户名和密码是否为空varusername =document.getElementById("Username").value;varpassword =document.getElementById("Password").value;if(!username || !password) {alert('用户名和密码不能为空');returnfalse; }// 验证是否同意协议varagreeCheckbox =document.getElementById...
JavaScript Can Validate Numeric Input JavaScript is often used to validate numeric input: Automatic HTML Form Validation HTML form validation can be performed automatically by the browser: If a form field (fname) is empty, therequiredattribute prevents this form from being submitted: ...
if (x === 0) { // Is `x` equal to zero? x = 123; } // Defining function `baz` with parameters `a` and `b` function baz(a, b) { return a + b; } 注意等号的两种不同用法: 单个等号(=)用于将一个值赋给一个变量。