I have a jsp page with some TextBoxes. Now I want to fill them with some information and click the submit button. But I need to check whether this TextBox is empty or not.
How can I do this?
This question is related to
javascript
Canonical without using frameworks with added trim prototype for older browsers
<html>
<head>
<script type="text/javascript">
// add trim to older IEs
if (!String.trim) {
String.prototype.trim = function() {return this.replace(/^\s+|\s+$/g, "");};
}
window.onload=function() { // onobtrusively adding the submit handler
document.getElementById("form1").onsubmit=function() { // needs an ID
var val = this.textField1.value; // 'this' is the form
if (val==null || val.trim()=="") {
alert('Please enter something');
this.textField1.focus();
return false; // cancel submission
}
return true; // allow submit
}
}
</script>
</head>
<body>
<form id="form1">
<input type="text" name="textField1" value="" /><br/>
<input type="submit" />
</form>
</body>
</html>
Here is the inline version, although not recommended I show it here in case you need to add validation without being able to refactor the code
function validate(theForm) { // passing the form object
var val = theForm.textField1.value;
if (val==null || val.trim()=="") {
alert('Please enter something');
theForm.textField1.focus();
return false; // cancel submission
}
return true; // allow submit
}
passing the form object in (this)
<form onsubmit="return validate(this)">
<input type="text" name="textField1" value="" /><br/>
<input type="submit" />
</form>
Using regexp: \S will match non whitespace character:anything but not a space, tab or new line. If your string has a single character which is not a space, tab or new line, then it's not empty. Therefore you just need to search for one character: \S
JavaScript:
function checkvalue() {
var mystring = document.getElementById('myString').value;
if(!mystring.match(/\S/)) {
alert ('Empty value is not allowed');
return false;
} else {
alert("correct input");
return true;
}
}
HTML:
<form onsubmit="return checkvalue(this)">
<input name="myString" type="text" value='' id="myString">
<input type="submit" value="check value" />
</form>
You can also check it using jQuery.. It's quite easy:
<html>
<head>
<title>jQuery: Check if Textbox is empty</title>
<script type="text/javascript" src="js/jquery_1.7.1_min.js"></script>
</head>
<body>
<form name="form1" method="post" action="">
<label for="city">City:</label>
<input type="text" name="city" id="city">
</form>
<button id="check">Check</button>
<script type="text/javascript">
$('#check').click(function () {
if ($('#city').val() == '') {
alert('Empty!!!');
} else {
alert('Contains: ' + $('#city').val());
}
});
</script>
</body>
</html>
Whatever method you choose is not freeing you from performing the same validation on at the back end.
<pre><form name="myform" 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>
Note: before using the code above you have to add the gen_validatorv31.js file.
Using this JavaScript will help you a lot. Some explanations are given within the code.
<script type="text/javascript">
<!--
function Blank_TextField_Validator()
{
// Check whether the value of the element
// text_name from the form named text_form is null
if (!text_form.text_name.value)
{
// If it is display and alert box
alert("Please fill in the text field.");
// Place the cursor on the field for revision
text_form.text_name.focus();
// return false to stop further processing
return (false);
}
// If text_name is not null continue processing
return (true);
}
-->
</script>
<form name="text_form" method="get" action="#"
onsubmit="return Blank_TextField_Validator()">
<input type="text" name="text_name" >
<input type="submit" value="Submit">
</form>
The most simple way to do it without using javascript is using required=""
<input type="text" ID="txtName" Width="165px" required=""/>
Source: Stackoverflow.com