Ways to check if a string is null, empty or equals an empty string ('')

emptyString.md

1. Using the typeof Operator and length Property:

• Check if the variable is a string and its length is 0

let str = "";
if (typeof str === "string" && str.length === 0) {
  console.log("The string is empty");
}

2. Using the length Property Directly:

• Directly check if the string's length is 0

let str = "";
if (str.length === 0) {
  console.log("The string is empty");
}

3. Using the trim Method:

• Remove leading and trailing whitespace characters before checking for emptiness:

let str = "     ";
if (str.trim().length === 0) {
  console.log("The string is empty");
}

4. Comparing with an Empty String:

let myStr = "";
if (myStr === "") {
  console.log("This is an empty String!");
}

5. Checking for Null Directly

let myStr = null;
if (myStr === null) {
  console.log("This is a null String!");
}

6. Combining Null and Empty Checks:

let myStr = null;
if (myStr === null || myStr.trim() === "") {
  console.log("This is an empty String!");
}

7. 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

let str = "";
if(str.replace(/\s/g,"") == ""){ 
  console.log("Empty String") 
} 

8. By Converting String to Boolean

let str = undefined;
if (Boolean(str) == false) {
    console.log("str is either null, empty, or undefined") 
}

9. Using strict equality operator

if (str === "" || str === null || str === undefined) {
   // string is not valid
} else {
   // string is valid
}

10. Creating a custom function that checks for null, undefined, empty strings, and strings that contain only whitespace characters:

function isEmpty(str) {
  // check if the string is null or undefined
  if (str === null || str === undefined) {
    return true;
  }
  
  // check if the string is an empty string or contains only whitespace characters
  return str.trim().length === 0;

}