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JavaScript: Return true if the parent element contains the child element, false otherwise

JavaScript fundamental (ES6 Syntax): Exercise-240 with Solution

Write a JavaScript program that will return true if the parent element contains the child element, false otherwise.

Note: Check that parent is not the same element as child, use parent.contains(child) to check if the parent element contains the child element.

  • Check that parent is not the same element as child.
  • Use Node.contains() to check if the parent element contains the child element.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
const elementContains = (parent, child) => parent !== child && parent.contains(child);

console.log(elementContains(document.querySelector('head'), document.querySelector('title')));
console.log(elementContains(document.querySelector('body'), document.querySelector('body')));

Sample Output:

false
false

Flowchart:

flowchart: Return true if the parent element contains the child element, false otherwise.

Live Demo:

See the Pen javascript-fundamental-exercise-240 by w3resource (@w3resource) on CodePen.


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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