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

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.

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 if value is empty in JavaScript

In JavaScript, you can check if a value is empty using several different methods, depending on the type of value you’re dealing with:

Checking for an empty string:

const myString = "";
if (myString === "") {
  // the string is empty
}

Checking for a null or undefined value:

let myVariable = null; // or let myVariable;
if (myVariable === null || myVariable === undefined) {
  // the value is null or undefined
}

Checking for an empty array:

const myArray = [];
if (myArray.length === 0) {
  // the array is empty
}

Checking for an empty object:

const myObject = {};
if (Object.keys(myObject).length === 0) {
  // the object is empty
}

Note that if you’re working with a string, you may also want to trim it before checking if it’s empty to ensure that any leading or trailing whitespace is removed:

const myString = "  ";
if (myString.trim() === "") {
  // the string is empty
}

It’s also worth noting that in JavaScript, an empty value, such as an empty string or null, is considered falsy, while a non-empty value is considered truthy. Therefore, you can also check for an empty value using an if statement with the double negation operator, which coerces the value to a boolean and returns its opposite:

const myString = "";
if (!!myString) {
  // the string is not empty
} else {
  // the string is empty
}

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

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