javascript check if field is empty – How To Add Validation For Empty Input Field with JavaScript?

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javascript check if field is empty – Checking if an input is empty with JavaScript – Use the === Operator to Check if the String Is Empty, Use the length Property to Check if the String Is Empty and Convert the Variable to Boolean to Check if the String Is Empty in JavaScript.

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javascript check if field is empty

Use the === Operator to Check if the String Is Empty in JavaScript

console.log(false === "")
console.log(undefined === "")
console.log(2 === "")
console.log(null === "")
console.log("Welcome Pakainfo!" === "")
console.log("" === "")

Check for an Empty String in JavaScript

const input = document.querySelector('input')
input.addEventListener('input', evt => {
  // Validate input
})

Example:

var userStr = ""
var memverStr = 0
var clientStr = false

console.log(userStr == "")
console.log(memverStr == "")
console.log(clientStr == "")

if input value is null do something

if(document.getElementById("interview_no").value.length == 0)
{
    alert("empty")
}

Use the length Property to Check if the String Is Empty in JavaScript

let userStr = "Welcome Pakainfo!";
let memverStr = "";
let clientStr = 4;
console.log(userStr.length === 0)
console.log(memverStr.length === 0)
console.log(clientStr.length === 0)

how to check if all inputs are not empty with javascript?

const inputFeilds = document.querySelectorAll("input");

const validInputs = Array.from(inputFeilds).filter( input => input.value !== "");

console.log(validInputs) //[array with valid inputs]

Convert the Variable to Boolean to Check if the String Is Empty in JavaScript

let userStr = "Welcome Pakainfo!";
let memverStr = "";
console.log(!!userStr)
console.log(!!memverStr)
console.log(Boolean(userStr))
console.log(Boolean(memverStr))

Check if value is empty in JavaScript

index.html

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initialscale=1.0">
<title>Check if value is empty in JavaScript - www.pakainfo.com </title>
<link rel="stylesheet" href="//code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css">
<script src="https://code.jquery.com/jquery-1.12.4.js"></script>
<script src="https://code.jquery.com/ui/1.12.1/jquery-ui.js"></script>
</head>
<body>
<form name="signup" onsubmit="return prodfileNameMember()">
memberNAME: <input type="text" name="membername">
<input type="submit" value="Save">
</form>
<script>
   function prodfileNameMember() {
      var membername = document.forms["signup"]["membername"].value;
      if (membername == null || membername == "") {
         alert("Please enter> the membername. Can’t be blank or empty !!!");
         return false;
      }
   }
</script>
</body>
</html>

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