How to check if a String is Empty in JavaScript

Check if a String is Empty in JavaScript #

Use the length property to check if a string is empty, e.g. if (str.length === 0) {}. If the string's length is equal to 0, then it's empty, otherwise it isn't empty.

index.js

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const str = '';

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

If you consider an empty string one that contains only spaces, use the trim() method to remove any leading or trailing whitespace before checking if it's empty.

index.js

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const str = '   ';

if (typeof str === 'string' && str.trim().length === 0) {
  console.log('string is empty');
} else {
  console.log('string is NOT empty');
}

The trim() method removes the leading and trailing spaces from a string. If the string contains only spaces, trim() returns an empty string.

To check if a string is truthy and contains one or more characters, pass the string to an if statement.

index.js

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const str = 'hello';

if (str) {
  // if this code block runs
  // 👉️ str is NOT "", undefined, null, 0, false, NaN
  console.log("string is truthy")
}

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.

You can also check that the value is not equal to an empty string.

index.js

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const str = '';

if (typeof str === 'string' && str !== '') {
  // if this code block runs
  // 👉️ string is NOT empty
}

We have 2 conditions in the if statement. We first check if the contents of the str variable are of type string. This is very important, because we shouldn't compare an empty string to a value of a different type.

We used the && (AND) operator to specify that both conditions have to be true for the if block to run.

This approach wouldn't work for a string that contains an empty space " ". If you need to handle strings that contain only spaces, use the trim() method.

index.js

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const str = '      ';

if (typeof str === 'string' && str.trim() !== '') {
  // if this code block runs
  // 👉️ string is NOT 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.

The String.trim method returns a new string with the whitespace from both ends of a string removed.

index.js

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const str = '     hello       ';

const trimmed  = str.trim();
console.log(trimmed) // 👉️ 'hello'

This is very useful when you're taking user input and want to make sure that the user didn't just enter a whitespace character to get around your validation.

We can check if a string is empty by accessing its length property. If the string has a length of 0, then it is empty.

index.js

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const str = 'hello';

if (typeof str === 'string' && str.length !== 0) {
  // if this code block runs
  // 👉️ string is NOT empty
  console.log("string is NOT empty")
}

Note that if you try to access the length property on a variable that is undefined or null you'd get an error. Make sure that the variable is set to a string before you try to access its length property.

How to check if a String is Empty in JavaScript

Check if a String is Empty in JavaScript #

Further Reading #

Borislav Hadzhiev