TypeError: toLocaleDateString is not a function in JS [Fix]

# TypeError: toLocaleDateString is not a function in JS

The "TypeError: toLocaleDateString is not a function" occurs when the toLocaleDateString() method is called on a value that is not a date object.

To solve the error, convert the value to a date before calling the method or make sure to only call the toLocaleDateString method on valid dates.

typeerror toLocaleDateString is not a function

Here is an example of how the error occurs.

index.js

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const d = Date.now();
console.log(d); // 👉️ 1639....

// ⛔️ TypeError: toLocaleDateString is not a function
const result = d.toLocaleDateString('en-US');

tolocaledatestring is not a function

We called the Date.now() function, which returns an integer and tried to call the Date.toLocaleDateString() method on it, which caused the error.

# Only call the `toLocaleDateString` method on valid Date objects

To solve the error, make sure to only call the toLocaleDateString() method on valid date objects.

index.js

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const d1 = new Date().toLocaleDateString('en-US');
console.log(d1);

const d2 = new Date('Sept 24, 22 13:20:18').toLocaleDateString(
  'en-US',
);
console.log(d2); // 👉️ 9/24/2022

only call tolocaledatestring on valid date objects

The code for this article is available on GitHub

You can get a date object by passing a valid date to the Date() constructor.

Note that if an invalid date is passed to the Date() constructor, you would get "Invalid date" back.

index.js

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const d1 = new Date('invalid').toLocaleDateString('en-US');
console.log(d1); // 👉️ "Invalid Date"

You can console.log the value you are calling the toLocaleDateString method on and see if it's a valid Date object.

# Check if the value is a valid Date before calling `toLocaleDateString`

You could conditionally check if the value is a Date object in the following way.

index.js

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const d1 = new Date();

if (
  typeof d1 === 'object' &&
  d1 !== null &&
  'toLocaleDateString' in d1
) {
  const result = d1.toLocaleDateString('en-US');
  console.log(result); // 👉️ 03/16/...
}

check if valid date before calling tolocaledatestring

The code for this article is available on GitHub

Our if condition uses the logical AND (&&) operator, so for the if block to run, all of the conditions have to be met.

We first check if the d1 variable stores a value with a type of object because dates have a type of object.

Then we check if the variable is not equal to null. Unfortunately, if you check the type of null - console.log(typeof null), you will get an "object" value back, so we have to make sure the value is not null.

index.js

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console.log(typeof null); // 👉️ object

The last thing we check for is that the object contains the toLocaleDateString property.

Then we know we can safely call the toLocaleDateString method on the object.

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TypeError: toLocaleDateString is not a function in JS [Fix]