用于空输入字段的 JavaScript 验证

我有这个输入框 <input name="question"/> I want to call IsEmpty function when submit clicking submit button.

我试了下面的代码，但没有工作。 有什么建议吗？

function IsEmpty() {


if (document.form.question.value == "") {
alert("empty");
}
return;
}
Question: <input name="question" /> <br/>


<input id="insert" onclick="IsEmpty();" type="submit" value="Add Question" />

803205 次浏览
小开

请参阅这里的工作示例

You are missing the required <form> element. Here is how your code should be like:

function IsEmpty() {
if (document.forms['frm'].question.value === "") {
alert("empty");
return false;
}
return true;
}
<form name="frm">
Question: <input name="question" /> <br />
<input id="insert" onclick="return IsEmpty();" type="submit" value="Add Question" />
</form>

小开

在您的输入元素中添加一个 id“ questions”，然后尝试这样做:

   if( document.getElementById('question').value === '' ){
alert('empty');
}

当前代码无法工作的原因是因为没有 FORM 标记。此外，不建议使用“ name”进行查找，因为它已被废弃。

见@Paul Dixon 在这篇文章中的回答: Is the 'name' attribute considered outdated for <a> anchor tags?

小开 
if(document.getElementById("question").value == "")
{
alert("empty")
}
小开

只需在输入元素中添加一个 ID 标记... ... 即:

并检查 javascript 中元素的值:

GetElementById (“ questions”) . value

哦，是的，得到 firefox/firebug。这是唯一的办法来做 javascript。

小开 
if(document.getElementById("question").value.length == 0)
{
alert("empty")
}
小开
最佳答案 

<script type="text/javascript">
function validateForm() {
var a = document.forms["Form"]["answer_a"].value;
var b = document.forms["Form"]["answer_b"].value;
var c = document.forms["Form"]["answer_c"].value;
var d = document.forms["Form"]["answer_d"].value;
if (a == null || a == "", b == null || b == "", c == null || c == "", d == null || d == "") {
alert("Please Fill All Required Field");
return false;
}
}
</script>


<form method="post" name="Form" onsubmit="return validateForm()" action="">
<textarea cols="30" rows="2" name="answer_a" id="a"></textarea>
<textarea cols="30" rows="2" name="answer_b" id="b"></textarea>
<textarea cols="30" rows="2" name="answer_c" id="c"></textarea>
<textarea cols="30" rows="2" name="answer_d" id="d"></textarea>
</form>

小开

一个输入字段 可以有空格，我们想要阻止这一点。
使用 Strim ():

function isEmpty(str) {
return !str.trim().length;
}

例如:

const isEmpty = str => !str.trim().length;


document.getElementById("name").addEventListener("input", function() {
if( isEmpty(this.value) ) {
console.log( "NAME is invalid (Empty)" )
} else {
console.log( `NAME value is: ${this.value}` );
}
});
<input id="name" type="text">

小开

如果用户禁用了 javascript，我想添加必需的属性:

<input type="text" id="textbox" required/>

它适用于所有现代浏览器。

小开 

<pre>
<form name="myform" action="saveNew" method="post" enctype="multipart/form-data">
<input type="text"   id="name"   name="name" />
<input type="submit"/>
</form>
</pre>


<script language="JavaScript" type="text/javascript">
var frmvalidator = new Validator("myform");
frmvalidator.EnableFocusOnError(false);
frmvalidator.EnableMsgsTogether();
frmvalidator.addValidation("name", "req", "Plese Enter Name");
</script>

在使用以上代码之前，您必须添加 Gen _ validatorv31. js 文件

小开

我下面的解决方案是在 es6，因为我利用了 const，如果你喜欢 es5，你可以用 var代替所有的 const。

const str = "       Hello World!        ";
// const str = "                     ";


checkForWhiteSpaces(str);


function checkForWhiteSpaces(args) {
const trimmedString = args.trim().length;
console.log(checkStringLength(trimmedString))
return checkStringLength(trimmedString)
}


// If the browser doesn't support the trim function
// you can make use of the regular expression below


checkForWhiteSpaces2(str);


function checkForWhiteSpaces2(args) {
const trimmedString = args.replace(/^\s+|\s+$/gm, '').length;
console.log(checkStringLength(trimmedString))
return checkStringLength(trimmedString)
}


function checkStringLength(args) {
return args > 0 ? "not empty" : "empty string";
}

小开

综合所有的方法，我们可以这样做:

const checkEmpty = document.querySelector('#checkIt');
checkEmpty.addEventListener('input', function () {
if (checkEmpty.value && // if exist AND
checkEmpty.value.length > 0 && // if value have one charecter at least
checkEmpty.value.trim().length > 0 // if value is not just spaces
)
{ console.log('value is:    '+checkEmpty.value);}
else {console.log('No value');
}
});
<input type="text" id="checkIt" required />

Note that if you truly want to check values you should do that on the server, but this is out of the scope for this question.

小开

您可以在提交后循环遍历每个输入，并检查它是否为空

let form = document.getElementById('yourform');


form.addEventListener("submit", function(e){ // event into anonymous function
let ver = true;
e.preventDefault(); //Prevent submit event from refreshing the page


e.target.forEach(input => { // input is just a variable name, e.target is the form element
if(input.length < 1){ // here you're looping through each input of the form and checking its length
ver = false;
}
});


if(!ver){
return false;
}else{
//continue what you were doing :)
}
})
小开 

<script type="text/javascript">
function validateForm() {
var a = document.forms["Form"]["answer_a"].value;
var b = document.forms["Form"]["answer_b"].value;
var c = document.forms["Form"]["answer_c"].value;
var d = document.forms["Form"]["answer_d"].value;
if (a == null || a == "", b == null || b == "", c == null || c == "", d == null || d == "") {
alert("Please Fill All Required Field");
return false;
}
}
</script>


<form method="post" name="Form" onsubmit="return validateForm()" action="">
<textarea cols="30" rows="2" name="answer_a" id="a"></textarea>
<textarea cols="30" rows="2" name="answer_b" id="b"></textarea>
<textarea cols="30" rows="2" name="answer_c" id="c"></textarea>
<textarea cols="30" rows="2" name="answer_d" id="d"></textarea>
</form>

小开

单击 Javascript 按钮时使用 HTML 验证定制输入消息

function msgAlert() {
const nameUser = document.querySelector('#nameUser');
const passUser = document.querySelector('#passUser');


if (nameUser.value === ''){
console.log('Input name empty!');
nameUser.setCustomValidity('Insert a name!');
} else {
nameUser.setCustomValidity('');
console.log('Input name ' + nameUser.value);
}
}


const v = document.querySelector('.btn-petroleo');
v.addEventListener('click', msgAlert, false);
.container{display:flex;max-width:960px;}
.w-auto {
width: auto!important;
}
.p-3 {
padding: 1rem!important;
}
.align-items-center {
-ms-flex-align: center!important;
align-items: center!important;
}
.form-row {
display: -ms-flexbox;
display: flex;
-ms-flex-wrap: wrap;
flex-wrap: wrap;
margin-right: -5px;
margin-left: -5px;
}
.mb-2, .my-2 {
margin-bottom: .5rem!important;
}
.d-flex {
display: -ms-flexbox!important;
display: flex!important;
}
.d-inline-block {
display: inline-block!important;
}
.col {
-ms-flex-preferred-size: 0;
flex-basis: 0;
-ms-flex-positive: 1;
flex-grow: 1;
max-width: 100%;
}
.mr-sm-2, .mx-sm-2 {
margin-right: .5rem!important;
}
label {
font-family: "Oswald", sans-serif;
font-size: 12px;
color: #007081;
font-weight: 400;
letter-spacing: 1px;
text-transform: uppercase;
}
label {
display: inline-block;
margin-bottom: .5rem;
}
.x-input {
background-color: #eaf3f8;
font-family: "Montserrat", sans-serif;
font-size: 14px;
}
.login-input {
border: none !important;
width: 100%;
}
.p-4 {
padding: 1.5rem!important;
}
.form-control {
display: block;
width: 100%;
height: calc(1.5em + .75rem + 2px);
padding: .375rem .75rem;
font-size: 1rem;
font-weight: 400;
line-height: 1.5;
color: #495057;
background-color: #fff;
background-clip: padding-box;
border: 1px solid #ced4da;
border-radius: .25rem;
transition: border-color .15s ease-in-out,box-shadow .15s ease-in-out;
}
button, input {
overflow: visible;
margin: 0;
}
.form-row {
display: -ms-flexbox;
display: flex;
-ms-flex-wrap: wrap;
flex-wrap: wrap;
margin-right: -5px;
margin-left: -5px;
}
.form-row>.col, .form-row>[class*=col-] {
padding-right: 5px;
padding-left: 5px;
}
.col-lg-12 {
-ms-flex: 0 0 100%;
flex: 0 0 100%;
max-width: 100%;
}
.mt-1, .my-1 {
margin-top: .25rem!important;
}
.mt-2, .my-2 {
margin-top: .5rem!important;
}
.mb-2, .my-2 {
margin-bottom: .5rem!important;
}
.btn:not(:disabled):not(.disabled) {
cursor: pointer;
}
.btn-petroleo {
background-color: #007081;
color: white;
font-family: "Oswald", sans-serif;
font-size: 12px;
text-transform: uppercase;
padding: 8px 30px;
letter-spacing: 2px;
}
.btn-xg {
padding: 20px 100px;
width: 100%;
display: block;
}
.btn {
display: inline-block;
font-weight: 400;
color: #212529;
text-align: center;
vertical-align: middle;
-webkit-user-select: none;
-moz-user-select: none;
-ms-user-select: none;
user-select: none;
background-color: transparent;
border: 1px solid transparent;
padding: .375rem .75rem;
font-size: 1rem;
line-height: 1.5;
border-radius: .25rem;
transition: color .15s ease-in-out,background-color .15s ease-in-out,border-color .15s ease-in-out,box-shadow .15s ease-in-out;
}
input {
-webkit-writing-mode: horizontal-tb !important;
text-rendering: auto;
color: -internal-light-dark(black, white);
letter-spacing: normal;
word-spacing: normal;
text-transform: none;
text-indent: 0px;
text-shadow: none;
display: inline-block;
text-align: start;
appearance: textfield;
background-color: -internal-light-dark(rgb(255, 255, 255), rgb(59, 59, 59));
-webkit-rtl-ordering: logical;
cursor: text;
margin: 0em;
font: 400 13.3333px Arial;
padding: 1px 2px;
border-width: 2px;
border-style: inset;
border-color: -internal-light-dark(rgb(118, 118, 118), rgb(195, 195, 195));
border-image: initial;
}
<div class="container">
<form name="myFormLogin" class="w-auto p-3 mw-10">
<div class="form-row align-items-center">
<div class="col w-auto p-3 h-auto d-inline-block my-2">
<label class="mr-sm-2" for="nameUser">Usuário</label><br>
<input type="text" class="form-control mr-sm-2 x-input login-input p-4" id="nameUser"
name="nameUser" placeholder="Name" required>
</div>
</div>
<div class="form-row align-items-center">
<div class="col w-auto p-3 h-auto d-inline-block my-2">
<label class="mr-sm-2" for="passUser">Senha</label><br>
<input type="password" class="form-control mb-3 mr-sm-2 x-input login-input p-4" id="passUser"
name="passUser" placeholder="Password" required>
<div class="help">Esqueci meu usuário ou senha</div>
</div>
</div>
<div class="form-row d-flex align-items-center">
<div class="col-lg-12 my-1 mt-2 mb-2">
<button type="submit" value="Submit" class="btn btn-petroleo btn-lg btn-xg btn-block p-4">Entrar</button>
</div>
</div>
<div class="form-row align-items-center d-flex">
<div class="col-lg-12 my-1">
<div class="nova-conta">Ainda não é cadastrado? <a href="">Crie seu acesso</a></div>
</div>
</div>
</form>
</div>

小开

下面的代码对我来说非常有效:

<form action = "dashboard.php" onsubmit= "return someJsFunction()">
<button type="submit" class="button"  id = "submit" name="submit" >Upload to live listing</button>
</form>
<script type="text/javascript">


function someJsFunction(){


const input = document.getElementById('input1');


if(input.value === ""){
alert ("no input?"); // This will prevent the Form from submitting
return false;
}else{
return true; // this will submit the form and handle the control to php.
}
}


</script>

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