JavaScript validation for empty input field
<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>An input field can have whitespaces, we want to prevent that.
Use String.prototype.trim():
function isEmpty(str) {
return !str.trim().length;
}
Example:
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">See the working example here
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>I would like to add required attribute in case user disabled javascript:
<input type="text" id="textbox" required/>
It works on all modern browsers.
if(document.getElementById("question").value.length == 0)
{
alert("empty")
}