Taken from Exercism
Your task is to figure out if a sentence is a pangram.
A pangram is a sentence using every letter of the alphabet at least once. It is case insensitive, so it doesn’t matter if a letter is lower-case (e.g.
k) or upper-case (e.g.K).For this exercise we only use the basic letters used in the English alphabet:
atoz.
Solution
This is the answer I came up with:
function isPangram(sentence: string): boolean {
// Create a Set from the alphabet
let alphabet: string = 'abcdefghijklmnopqrstuvwxyz'
let alphaSet: Set<string> = new Set([...alphabet])
// Convert the sentence to lowercase, filter against the alphabet Set
let rawSentenceArray: Array<string> = [...sentence.toLowerCase()]
let filteredSentenceArray: Array<string> = []
rawSentenceArray.forEach(element => {
if (alphaSet.has(element)) {
filteredSentenceArray.push(element)
}
})
// Convert the filtered sentence Array into a Set,
let sentenceSet: Set<string> = new Set([...filteredSentenceArray])
// Compare the two Sets via number of elements (since 26 chars in alphabet)
return (sentenceSet.size === alphaSet.size) ? true : false
}The tests checked for underscores, numbers, and punctuation but the implementation covered all edge cases since filtering against a Set is discriminative.