w3resource

JavaScript: Check whether the provided value is of the specified type

JavaScript fundamental (ES6 Syntax): Exercise-208 with Solution

Write a JavaScript program to check whether the provided value is of the specified type.

  • Ensure the value is not undefined or null using Array.prototype.includes().
  • Compare the constructor property on the value with type to check if the provided value is of the specified type.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
const is = (type, val) => ![, null].includes(val) && val.constructor === type;
console.log(is(Array, [1])); // true
console.log(is(ArrayBuffer, new ArrayBuffer()));
console.log(is(Map, new Map()));
console.log(is(RegExp, /./g));
console.log(is(Set, new Set()));
console.log(is(WeakMap, new WeakMap()));
console.log(is(WeakSet, new WeakSet()));
console.log(is(String, ''));
console.log(is(String, new String('')));
console.log(is(Number, 1));
console.log(is(Number, new Number(1)));
console.log(is(Boolean, true));
console.log(is(Boolean, new Boolean(true)));

Sample Output:

true
true
true
true
true
true
true
true
true
true
true
true
true

Flowchart:

flowchart: Check whether the provided value is of the specified type.

Live Demo:

See the Pen javascript-basic-exercise-208-1 by w3resource (@w3resource) on CodePen.


Improve this sample solution and post your code through Disqus

Previous: Write a JavaScript program to that will return true if the given string is an absolute URL, false otherwise.
Next: Write a JavaScript program to get a list of elements that exist in both arrays, using a provided comparator function.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.



Follow us on Facebook and Twitter for latest update.