TypeError: trim is not a function in JavaScript [Solved]

# TypeError: trim is not a function in JavaScript

The "TypeError: trim is not a function" error occurs when we call the trim() method on a value that is not a string.

To solve the error, convert the value to a string using the toString() method or make sure to only call the trim method on strings.

Here is an example of how the error occurs.

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const arr = [' hey ', ' there '];

// ⛔️ TypeError: trim is not a function
arr.trim();

We called the String.trim() method on an array, which caused the error.

# Make sure to only call the trim() method on strings

To solve the error, make sure to only call the trim() method on strings.

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const str = ' hello ';

const result = str.trim();

console.log(result); // 👉️ "hello"

The trim() method removes the leading and trailing whitespace from the string.

# Check if the value is of type string before calling trim()

Alternatively, you can check if the value is a string before calling the trim() method.

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const str = null;

const result = typeof str === 'string' ? str.trim() : '';

console.log(result); // 👉️ ""

We used the ternary operator to check if the str variable stores a string.

If it does, the value to the left of the comma is returned, otherwise, the value to the right is returned.

You can also use a simple if statement to achieve the same result.

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const str = null;

let result = '';

if (typeof str === 'string') {
  result = str.trim();
}

console.log(result); // 👉️ ""

# Call the trim() method on all strings in an Array

If you want to trim all strings in an array, use the Array.map() method to iterate over the array and call the trim() method on each string.

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const arr = [' bobby ', ' hadz ', '  com  '];

const result = arr.map(str => str.trim());

// 👇️ [ 'bobby', 'hadz', 'com' ]
console.log(result);

The function we passed to the Array.map() method gets called with each element in the array.

On each iteration, we call the String.trim() method on the current element and return the result.

The map() method returns a new array containing the values returned from the callback function.

If the error persists, console.log the value you're calling the trim method on and check its type using the typeof operator.

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console.log(typeof 'bobbyhadz.com'); // 👉️ string
console.log(typeof null); // 👉️ object
console.log(typeof {}); // 👉️ object

If the value is an object, there's a very good chance that you are forgetting to access a specific property, on which you need to call the trim() method.

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// ✅ with Objects
const obj = {
  site: '   bobbyhadz.com   ',
};

const result1 = obj.site.trim();
console.log(result1); // 👉️ "bobbyhadz.com"

// -------------------------------------------

// ✅ with Arrays

const arr = ['   bobby  ', '  hadz  ', '  com '];

const result2 = arr[0].trim();
console.log(result2); // 👉️ "bobby"

We accessed a property in the object and an element in the array before calling the String.trim() method.