Solutions For The Error “TypeError: getMonth() is not a function” In JavaScript

To fix the error “TypeError: getMonth() is not a function” in JavaScript, you need to know why your program throws the above error, then know how to fix it with a specific reason, and fixing it will be faster and more accurate. Let’s read this article now.

Why is the error “TypeError: getMonth() is not a function” in JavaScript happening?

There are quite a few common reasons when your program throws the error “TypeError: getMonth() is not a function” in Javascript like:

• Misuse of getMonth() method
• Create a date without using the ‘new’ operator
• Call the getMonth() method from a value other than a date

The error message occurs as follows:

Uncaught TypeError: getMonth() is not a function

These are examples of code that causes the above error:

var obj = {
	property: "value",
};

// Wrong syntax of getMonth() method
var d1 = new Date("12 / 2 / 2022").Getmonth();

// Create a date without using the 'new' operator
var d2 = Date("12 / 2 / 2022").getMonth();

// Call the getMonth() method from a value other than a date
var d3 = obj.getMonth();

How to fix the error “TypeError: getMonth() is not a function” in JavaScript?

Wrong syntax of getMonth() method

First, we should check whether the syntax when we use getMonth() method is correct. If it is correct and still has an error, we should study other causes.

Syntax:

Date.getMonth()

Try replacing the date with the date you want to get its month to see if there is still an error. If it’s over, then congratulations. If not, try the following two reasons to find a solution.

Create a date without using the ‘new’ operator

To fix this error, we need to add the new operator when initializing a new date, so this error will no longer appear.

Example:

var d2 = new Date("12 / 2 / 2022").getMonth();
console.log(d2);

Output:

11

When we add the new operator, the program usually runs and outputs the expected result.

Call the getMonth() method from a value other than a date

To determine if the variable that calls the getMonth() method has a value of a date or not, we will use an If statement to perform a check of the conditions to see if it is considered a date value, as shown below:

function isDate(date) {
	if (date instanceof Date && !isNaN(date.valueOf())) {
		return true;
	}
	return false;
}

We try using the above function to check. Then we try to use the getMonth() method with two cases of valid Date and invalid Date to see whether the function works as expected.

Example 1:

var date = new Date(); // 04/12/2022

function isDate(date) {
	if (date instanceof Date && !isNaN(date.valueOf())) {
		return true;
	}
	return false;
}

if (isDate(date)) {
	console.log(date.getMonth());
} else {
	console.log("This is not a Date");
}

Output:

11

Example 2:

var obj = {
	property: "value",
};

function isDate(date) {
	if (date instanceof Date && !isNaN(date.valueOf())) {
		return true;
	}
	return false;
}

if (isDate(obj)) {
	console.log(obj.getMonth());
} else {
	console.log("This is not a Date");
}

Output:

This is not a Date

The function works very well whether the date is valid or not.

Summary

To sum up, I have given a few common reasons, and ways to fix the error “TypeError: getMonth() is not a function” in JavaScript. I hope this article helps you and your program and wish you success.

Maybe you are interested:

• TypeError: date.getHours is not a function in JavaScript
• TypeError: map.get is not a function in JavaScript
• TypeError: Cannot set Property which has only a Getter in JavaScript

Tom Joseph

My name is Tom Joseph, and I work as a software engineer. I enjoy programming and passing on my experience. C, C++, JAVA, and Python are my strong programming languages that I can share with everyone. In addition, I have also developed projects using Javascript, html, css.

Job: Developer
Name of the university: UTC
Programming Languages: C, C++, Javascript, JAVA, python, html, css