问题描述
<html lang="en">
<head>
<Meta charset="UTF-8">
<Meta name="viewport" content="width=device-width,initial-scale=1.0">
<title>Document</title>
</head>
<body>
<h1>To Do List</h1>
<form>
<input autocomplete="off" autofocus id="todotext"
type="text">
<input onclick="serve(); return false" type="submit">
</form>
<ol id="add"></ol>
</body>
<script>
function serve(){
const neww = document.getElementById('add');
let text = document.getElementById('todotext').value;
const a = document.createElement('li');
a.innerText = text;
neww.appendChild(a);
document.getElementById('todotext').value = "";
}
</script>
</html>
这是我的代码,如果有人提交空表单,我想返回一个“警报”。 我该怎么做?任何帮助将不胜感激
这是一张图片:
解决方法
String.prototype.isEmpty = function() {
return (this.length === 0 || !this.trim());
};
function serve(){
const neww = document.getElementById('add')
let text = document.getElementById('todotext').value;
if( text.isEmpty() ){
alert('cannot be blank');
return;
}
const a = document.createElement('li')
a.innerText = text
neww.appendChild(a)
document.getElementById('todotext').value = ""
}
<h1>To Do List</h1>
<form>
<input autocomplete="off" autofocus id="todotext"
type="text">
<input onclick="serve(); return false" type="submit">
</form>
<ol id="add"></ol>
通过检查 todoText 的值添加新元素时的条件
function serve(){
const neww = document.getElementById('add')
let text = document.getElementById('todotext').value
if(text == ""){
alert('field is required');
}
else{
const a = document.createElement('li')
a.innerText = text
neww.appendChild(a)
document.getElementById('todotext').value = ""
};
}
,这是你想要的吗?
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,initial-scale=1.0">
<title>Document</title>
</head>
<body>
<h1>To Do List</h1>
<form>
<input autocomplete="off" autofocus id="todotext"
type="text">
<button onclick="todotext.value != '' ? serve() : alert('Input field is blank')" >Submit</button>
</form>
<ol id="add"></ol>
</body>
<script>
var todotext = document.getElementById('todotext');
function serve() {
const neww = document.getElementById('add');
let text = todotext.value;
const a = document.createElement('li');
a.innerText = text;
neww.appendChild(a);
document.getElementById('todotext').value = "";
}
</script>
</html>
,
function serve(){
const neww = document.getElementById('add')
let text = document.getElementById('todotext').value
if(text.trim().length === 0){
alert("Field is empty");
}else{
const a = document.createElement('li')
a.innerText = text
neww.appendChild(a)
document.getElementById('todotext').value = ""
}
}
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,initial-scale=1.0">
<title>Document</title>
</head>
<body>
<h1>To Do List</h1>
<form>
<input autocomplete="off" autofocus id="todotext"
type="text">
<input onclick="serve(); return false" type="submit">
</form>
<ol id="add"></ol>
</body>
</html>