How to Check if a JavaScript Variable is a Function?

Checking for Function Type Variables

Background: When working with JavaScript, it is often useful to determine the type of a variable to ensure appropriate handling. This article explores how to check if a variable is of function type, which represents functions stored as variables.

Implementation:

To determine if a variable is of function type, JavaScript provides the typeof operator. The operator returns the type of the variable as a string. In the case of function-type variables, typeof will return the string 'function'.

The following function demonstrates how to check the type of a variable using typeof:

<code class="javascript">function foo(v) {
  if (typeof v === 'function') {
    // do something
  }
}</code>

To use the function, simply pass the variable you wish to check as its argument. For instance:

<code class="javascript">var a = function() { /* Statements */ };
foo(a); // Executes the if statement because 'a' is a function</code>

By utilizing this method, you can effectively determine whether a JavaScript variable is a function, allowing you to handle function-type variables appropriately within your code.

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