How to Check if a String Is Empty, Undefined or Null in Javascript?

javascript

JavaScript provides a number of ways to check if a string is empty or if a variable is undefined or null. Here are a few examples:

1. Check for an empty string:

let str = "";

if (str === "") {
  console.log("string is empty");
}

2. Check for undefined variable:

let val;

if (typeof val === "undefined") {
  console.log("variable is undefined");
}

3. Check for null variable:

let val = null;

if (val === null) {
  console.log("variable is null");
}

4. Check for empty or undefined string using ternary operator:

let str;

const result = str ? str : "default value";
console.log(result); // Output: "default value"

5. Check for empty or undefined string using logical OR operator:

let str;

const result = str || "default value";
console.log(result); // Output: "default value"

Note: Keep in mind that the triple equal (===) operator is used to check for both type and value while the double equal (==) operator only checks for value.

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