How to check if a String is Empty in JavaScript

# Check if a String is Empty in JavaScript

Use the length property on the string to check if it is empty.

If the string's length is equal to 0, then it's empty, otherwise, it isn't empty.

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const str = '';

if (typeof str === 'string' && str.length === 0) {
  // 👇️ this runs
  console.log('The string is empty');
} else {
  console.log('The string is NOT empty')
}

The String.length property returns the number of characters in the string.

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console.log(''.length); // 👉️ 0
console.log('a'.length); // 👉️ 1
console.log('ab'.length); // 👉️ 2

If accessing the string's length property returns 0, then the string is empty.

If you have to do this often, define a reusable function.

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function isEmpty(string) {
  return typeof string === 'string' && string.length === 0;
}

console.log(isEmpty('')); // 👉️ true
console.log(isEmpty('a')); // 👉️ false
console.log(isEmpty('ab')); // 👉️ false

if (isEmpty('')) {
  // 👇️ this runs
  console.log('The string is empty');
} else {
  console.log('The string is NOT empty');
}

The function takes a string as a parameter and returns true if the string is empty and false otherwise.

# Handling strings that only contain spaces

If you also consider an empty string one that contains only spaces, use the String.trim() method before checking if the string is empty.

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const str = '   ';

if (typeof str === 'string' && str.trim().length === 0) {
  // 👇️ this runs
  console.log('The string is empty');
} else {
  console.log('THe string is NOT empty');
}

The String.trim() method removes the leading and trailing whitespace from a string and returns a new string, without modifying the original string.

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const str = '        ';
console.dir(str.trim()); // 👉️ ""

console.dir(str.length); // 👉️ 8

console.dir(str.trim().length); // 👉️ 0

The trim() method removes all whitespace characters including spaces, tabs and newlines.

You can also use the optional chaining (?.) operator if you need to handle null and undefined values.

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const str = '            ';

if (str?.trim()) {
  console.log('The string is NOT empty');
} else {
  // 👇️ this runs
  console.log('The string is empty');
}

The optional chaining (?.) operator short-circuits and returns undefined if the value to the left is nullish (null or undefined).

This handles a scenario where the str variable stores an undefined value.

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const str = undefined;

if (str?.trim()) {
  console.log('The string is NOT empty');
} else {
  // 👇️ this runs
  console.log('The string is empty');
}

Instead of getting an error for trying to call the trim() method on an undefined value, the call short-circuits, returning undefined because we used the optional chaining (?.) operator.

# Checking if a string isn't empty

Use the value in an if statement to check if it is truthy.

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const str = 'bobbyhadz.com';

if (str) {
  // if this code block runs
  // str is NOT "", undefined, null, 0, false, NaN
  console.log('The value is truthy');
} else {
  console.log(
    'The value is undefined, null 0, false, NaN or empty string',
  );
}

The code in the if block wouldn't run if the str variable is set to an empty string, undefined, null, 0, false or NaN.

All other values are truthy.

You can also check that the value isn't equal to an empty string.

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const str = '';

if (typeof str === 'string' && str !== '') {
  console.log('The string is NOT empty');
} else {
  // 👇️ this runs
  console.log('The string is empty');
}

We used the logical AND (&&) operator to chain 2 conditions. Both conditions have to be met for the if block to run.

1. The first condition checks that the value is a string.
2. The second checks that the string isn't empty.

# Checking if a string isn't empty or contains only whitespace

This approach wouldn't work for a string that contains only spaces.

If you need to handle strings that contain only spaces, use the trim() method.

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const str = '      ';

if (typeof str === 'string' && str.trim() !== '') {
  console.log('The string is NOT empty');
} else {
  // 👇️ this runs
  console.log('The string is empty');
}

We first make sure that the str variable contains a string and then we call the String.trim() method.

If we try to call the trim method on a variable that is set to undefined or null, we'd get an error.

# Checking if a value is falsy

If you need to check for a falsy value, use the logical NOT (!) operator.

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const str = 'bobbyhadz.com';

if (!str) {
  console.log(
    'The value is undefined, null 0, false, NaN or empty string',
  );
} else {
  // 👉️ str is NOT "", undefined, null, 0, false, NaN
  console.log('The string is truthy');
}

The if block is only run if the str variable stores a falsy value.

The falsy values in JavaScript are: false, 0, empty string "", null, undefined and NaN (not a number).

All other values are truthy.

# Checking if a value is an empty string, undefined or null

You can use the logical OR (||) operator if you want to explicitly check if a variable stores an empty string, undefined or null.

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const str = '';

if (typeof str === undefined || str === null || str === '') {
  // 👇️ this runs
  console.log('The value is undefined, null or empty string');
} else {
  console.log(
    'The value is NOT undefined, null or empty string',
  );
}

We used the logical OR (||) operator, so the if block is run if either condition is met.

The if block in the example runs if the str variable stores undefined, null or an empty string.

# Checking if a value is NOT an empty string, undefined or null

Conversely, you can use the logical AND (&&) operator to check if a variable doesn't store an empty string, null or undefined.

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const str = 'bobbyhadz.com';

if (typeof str !== undefined && str !== null && str !== '') {
  // 👇️ this runs
  console.log(
    'The value is NOT undefined, null or empty string',
  );
} else {
  console.log('The value is undefined, null or empty string');
}

We used the logical AND (&&) operator, so for the if block to run, all conditions have to be met.

We check that:

1. The variable doesn't store an undefined value.
2. The variable doesn't store a null value.
3. The variable is not an empty string.

# Checking if a value is empty using lodash

If you use the lodash module, you can also use the isEmpty() method to check if a value is empty.

If you need to install lodash, run the following command.

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# 👇️ initialize a package.json file
npm init -y

npm install lodash

You can now import and use the lodash.isEmpty() method.

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import _ from 'lodash';

console.log(_.isEmpty(null)); // 👉️ true
console.log(_.isEmpty(undefined)); // 👉️ true
console.log(_.isEmpty('')); // 👉️ true
console.log(_.isEmpty([])); // 👉️ true
console.log(_.isEmpty({})); // 👉️ true
console.log(_.isEmpty(true)); // 👉️ true

console.log(_.isEmpty('abc')); // 👉️ false
console.log(_.isEmpty(['a', 'b'])); // 👉️ false
console.log(_.isEmpty({a: 'b'})); // 👉️ false

The isEmpty() method returns true if the value is an empty string, null, undefined, an empty object, collection, Map or Set.

Array-like objects, buffers and strings are considered empty if they have a length of 0.

Similarly, Map and Set objects are considered empty if they have a size of 0.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

• Create a String of length N filled with repeated char in JS
• Get the first Character of a String in JavaScript
• Prevent a button from submitting the form using JavaScript