JavaScriptDetectCapital.md

JavaScript Detect Capital

Challenge

Usage of capitals in a word will be deemed correct when one of the following cases is met:

• All letters in the word are capitals, like 'SUPERKLOK' for instance.
• All letters in the word are not capitals, such as 'superklok'.
• Only the first letter in the word is capitalized, as in 'Superklok'.

Given a string word, return true if the usage of capitals in it is correct.

1^st Example

Input: word = 'SUPERKLOK'
Output: true

2^nd Example

Input: word = 'SuPeRkLoK'
Output: false

Constraints

• 1 <= word.length <= 100
• word consists of lowercase and/or uppercase English letters.

Solution

const detectCapitalUse = function(word) {
    return (word === word.toUpperCase() ||
            word === word.toLowerCase() ||
            word === word[0].toUpperCase() +
            word.slice(1).toLowerCase());
};

Explanation

I've decided to use the OR operator to return a Boolean based on three different acceptable condition possibilities.

The first condition will return true if the word is truly equal to the word with the toUpperCase method applied which transforms the string into all capital letters. This validates that the word is correctly written in all capitals.

The second condition will return true if the word is truly equal to the word with the toLowerCase method applied which transforms the string into all lowercase letters. This validates that the word isn't using any capital letters and it's written entirely in lowercase.

The final condition will return true if the letter at index 0 of the word (the first letter of the string) is the same as the first letter of the word with the toUpperCase method applied, and that all the letters from index 1 to the end of the word (the second letter and all letters that follow it) are equivalent to the letters of the word at those indexes but with the toLowerCase method applied. This validates that the word is only using a capitalized character as the first letter of the word and all the other letters that follow are written in lowercase.

If none of the above three conditions are met, then the function returns false to indicate that the capitalized characters are not being used correctly in the test string.

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