How do I filter out a string to contain only letters in vanilla Javascript?

Question

I was given this string:

var myMessage = "Learning is fun!"

This is how I attempted to create an array listing only the letters (without the spaces and "!").

var myMessage = "Learning is fun!";
var arr1 = myMessage.split("");

function onlyLetters(array){
    let arr2 = []
    for(let i = 0; i < array.length; i++){
        if(array[i] === "a" || "b" || "c" || "d" || "e" 
        || "f" || "g" || "h" || "i" || "j" || "k" || "l" 
        || "m" || "n" || "o" || "p" || "q" || "r" || "s" 
        || "t" || "u" || "v" || "w" || "x" || "y" || "z"){
          arr2.push(array[i])
        }
    }
    return arr2
}

console.log(onlyLetters(myMessage))

What am I doing wrong? Also, is there a shorthand for listing letters "a" through "z"?

Solution

A simple way may be to use Regex like so

let message = "Learning is fun!";
let onlyLettersArray = message.split('').filter(char => /[a-zA-Z]/.test(char));
console.log(onlyLettersArray)

.filter takes an array and runs a function on the elements, which returns true or false. The item is removed if it returns false. The regex checks if the character is within the range a-z or A-Z

Another way is to filter the char and then split it like so

let message = "Learning is fun!";
let onlyLettersArray = message.replace(/[^a-z]+/gi, '').split('');
console.log(onlyLettersArray)

Edit:

var myMessage = "Learning is fun!";
var arr1 = myMessage.split("");

function onlyLetters(array){
    let arr2 = []
    for(let i = 0; i < array.length; i++){
        if(/[a-z]/.test(array[i])){ // you can use regex instead of all characters
          arr2.push(array[i])
        }
    }
    return arr2
}

console.log(onlyLetters(myMessage))

Update: If instead of an array of characters, you have to replace special chars in a string, you can write

let message = "Learning is fun!";
let letterMessage = message.replace(/[^a-zA-Z]/gm,"")
console.log(letterMessage)

Comments

[ninesalt]

You can't do array[i] === "a" || "b" || .... because the right side of the === is evaluated as "a" || "b" || .... . What you mean to do is array[i] === "a" || array[i] === "b" || ...

[ninesalt]

I'd argue that since OP is a beginner, it is more helpful to them to help with their existing code rather than give them something new.

[Dhananjai Pai]

I have given the explanation as well. I believe it may be a good way for them to learn the features javascript can offer as well. But you do have a valid point and I will update the code to add what the OP has used

[Dhananjai Pai]

I think he wanted an array of characters based on the question. If it is a string, you could replace the special chars @AZ_

[Dhananjai Pai]

He hasn't used a join() in the end

[ninesalt]

You can also do message.replace(/[^a-z]+/gi, '').split('')

[Dhananjai Pai]

it is String.prototype.match. Not array

[AZ_]

@DhananjaiPai oops! typo

[Dhananjai Pai]

yeah @ninesalt that makes more sense too