How to Check for an Empty String in JavaScript

Use the === Operator

You can use the strict equality operator (===) to check whether a string is empty or not.

The comparsion str === "" will only return true if the data type of the value is string and it is not empty, otherwise return false as demonstrated in the following example:

<script>
if(str === ""){
    // string is empty, do something
}
    
// Some test cases
alert(2 === "");  // Outputs: flase
alert(0 === "") // Outputs: false
alert("" === "") // Outputs: true
alert("Hello World!" === "") // Outputs: false 
alert(false === "") // Outputs: false
alert(null === "") // Outputs: false
alert(undefined === "") // Outputs: false
</script>

As you can see the values null, undefined, false returns false in the comparision, because they are special values.