freeCodeCamp Challenge Guide :Basic Algorithm Scripting: Mutations

Using Regular Expression( RegExp) as a solution.

function mutation(arr) {
return arr[1].match(RegExp(`[${arr[0]}]`,'gi')).length===arr[1].length;

Code Explanation

Created a Regular Expression using The RegExp constructor function with [] which Match any character in the set, with global search g and ignore case i flags.

The match() method retrieves all elements that were matched using with the RegExp in an array format.
The length property of an object which is an instance of type Array sets or returns the number of elements in that array.
The strict equality operator (===) checks whether its two operands are equal, returning a Boolean result.

In short, we create RegExp using all the characters from index 0 of the array and find which characters which match with characters from index 1 of the array.
A new array is created with all the matched characters.
We get length of that new array and compare it with the length from the original array of index 1. If both length match (True) else (False).

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