JavaScript: Check if a given argument is a number

JavaScript fundamental (ES6 Syntax): Exercise-195 with Solution

Check If Number

Write a JavaScript program to check if a given argument is a number.

• Use typeof to check if a value is classified as a number primitive.
• To safeguard against NaN, check if val === val (as NaN has a typeof equal to number and is the only value not equal to itself).

Sample Solution:

JavaScript Code:

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

// Test cases to check if the values are numbers
console.log(isNumber('1'));  // false (the value is a string, not a number)
console.log(isNumber(1));    // true (the value is a number)

Output:

false
true

Visual Presentation:

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-195-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that returns true if the provided value is a finite number.
• Write a JavaScript function that verifies an input is a number by using typeof and isNaN checks.
• Write a JavaScript program that distinguishes between numeric strings and actual numbers, returning a boolean.
• Write a JavaScript function that uses Number.isFinite to confirm that a value is a valid number.

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