Why JavaScript error “is not a function” occurs

JavaScript error “is not a function” is pretty straight forward. Sometime you will get Uncaught TypeError. So the question is why this type of error occurs?

Suppose you declared a variable i.e x and call it as JavaScript Function i.e x(), then you will get this type of error. Let’s take an example-

function foo(){
	var bar = 5;
	bar();
}

In the above function, you declared a variable bar with a value 5, and the next line you called the variable as a function. So you will get Uncaught TypeError: bar is not a function.

You may also like to read: Check if a string contains a specific word in PHP?

Another example of JavaScript error “is not a function” is-

Suppose If you have created a function called setCounter(), and you call it like setCountar(). So there is no function exist in your code called setCountar(). Basically this is a spelling mistake. So you will get the error Uncaught TypeError: setCountar is not a function.

So this type of error generally occurs if you make a spelling mistake or if you try to call a variable as a function.

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