If we want to check any string either it is filled or empty we can use Javascript for such purpose for example : form validation.
Example :
html
<script> function checkempty(form) { if (form.name.value == null || form.name.value == undefined || form.name.value.length == 0) { alert("Name cannot be empty\n"); return false; } else { alert("Your response has been recorded\n"); return true; } } </script> <form onsubmit="return checkempty(form1)" action="#" method="post" name="form1"> <label>Enter your name</label> <br> <input type="string" placeholder="Enter name" name="name" /> <br> <br> <label>Enter Email</label> <br> <input type="" placeholder="Enter email" name="email" /> <br> <br> <label>Enter password</label> <br> <input type="password" placeholder="Enter password " name="password1" /> <br> <br> <label>Confirm password</label> <br> <input type="password" placeholder="Enter password " name="password2" /> <br> <br> <input type="submit" value="submit" /> <br> </form> |
Output: If the name is empty.
How to check empty/undefined/null string in JavaScript?
Simplified with 3 Different Methods
Method 1: Using === operator
Using === operator we will check the string is empty or not. If empty then it will return “Empty String” and if the string is not empty it will return “Not Empty String”
Javascript
// function to check string is empty or not function checking(str){ // checking the string using === operator if (str === "") { console.log("Empty String") } else { console.log("Not Empty String") } } // calling the checking function with empty string checking("") // calling the checking function with not an empty string checking("neveropen") |
Output:
Empty String Not Empty String
Method 2: By using the length and ! operator
This function will check the length of the string also by using ! operator we will check string is empty or not.
Javascript
// function to check string is empty or not function checking(str) { // checking the string using ! operator and length // will return true if empty string and false if string is not empty return (!str || str.length === 0 ); } // calling the checking function with empty string console.log(checking("")) // calling the checking function with not an empty string console.log(checking("neveropen")) |
Output:
true false
Method 3: By using replace
It will ensure that the string is not just a group of empty spaces where we are doing replacement on the spaces.
Javascript
// function to check string is empty or not function checking(str){ if(str.replace(/\s/g,"") == ""){ console.log("Empty String") } else{ console.log("Not Empty String") } } // calling the checking function with empty string checking(" ") // calling the checking function with not an empty string checking("Hello Javascript") |
Output:
Empty String Not Empty String
