JavaScript: Return true if the specified value is undefined, false otherwise
JavaScript fundamental (ES6 Syntax): Exercise-185 with Solution
Write a JavaScript program that will return true if the specified value is undefined, false otherwise.
Note: Use the strict equality operator to check if the value and of val are equal to undefined.
- Use the strict equality operator to check if val is equal to undefined.
Sample Solution:
JavaScript Code:
//#Source https://bit.ly/2neWfJ2
const isUndefined = val => val === undefined;
console.log(isUndefined(undefined));
Sample Output:
true
Flowchart:

Live Demo:
See the Pen javascript-basic-exercise-185-1 by w3resource (@w3resource) on CodePen.
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Next: Write a JavaScript program to check if the given argument is a symbol.
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JavaScript: Tips of the Day
How to check whether a string contains a substring in JavaScript?
ECMAScript 6 introduced String.prototype.includes:
const string = "foo"; const substring = "oo"; console.log(string.includes(substring));
includes doesn't have Internet Explorer support, though. In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found:
var string = "foo"; var substring = "oo"; console.log(string.indexOf(substring) !== -1);
Ref: https://bit.ly/3fFFgZv
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