Hi! I'm Mayu.
In this post, I introduce how to change letter's case in JavaScript.

Now, here is a sentence about me.

i LOVE JaVa SpaRRoW!

How do you feel when you read this sentence?
A little weird...is it?
(By the way, recently I realized this is an expression of interesting intonation. I didn't know this before I started learning English, so I am happy about this realization!)

So, let's make function to the sentence to be more readable :)✨

function changeLetter(text) {
    let word = text.split(" ");
    let arr =[];
    for(let i= 0; i < word.length; i++){
        arr.push(word[i].charAt(0).toUpperCase() + word[i].substring(1).toLowerCase());
    }
    return arr.join(" ");
}

console.log(changeLetter('i LOVE JaVa SpaRRoW!'));
// I Love Java Sparrow!

1. Set space as separater and split sentences into words.

• split() to split sentence with spaces(" ").

2. Add elements that capitalized only the first letter to the array.

• use loop because each texts have more than 2 words.
• charAt() method that returns new string
• toUpperCase() method returns the calling string value converted to uppercase
• substring() method that returns the part of the string
• toLowerCase() method returns the calling string value converted to lowercase
• push() method that adds elements to the end of an array

3. Return to a sentence with a space between words.

• join() method creates and returns a new string by concatenating all of the elements in an array, separated by commas or a specified separator string.

reference: mdn