JavaScript: Check whether the given argument is a function

JavaScript fundamental (ES6 Syntax): Exercise-198 with Solution

Check If Function

Write a JavaScript program to check whether the given argument is a function.

• Use typeof to check if a value is classified as a function primitive.

Sample Solution:

JavaScript Code:

// Define a function 'isFunction' that checks if the given value 'val' is a function
const isFunction = val =>
  // Check if the type of the given value 'val' is 'function'
  typeof val === 'function';

// Test cases to check if the values are functions
console.log(isFunction('x'));      // false (the value is not a function)
console.log(isFunction(x => x));   // true (the value is a function)

Output:

false
true

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-198-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that returns true if the provided argument is a function using typeof.
• Write a JavaScript function that tests whether a variable is callable by checking its constructor and prototype.
• Write a JavaScript program that distinguishes functions from objects by using Object.prototype.toString().
• Write a JavaScript function that validates an input and logs a message if it is not a function.

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