Strings

String is a sequence of symbols. All of the symbols can be accessed via their indexes starting from 0.

Indexes

Let's say we have the string "computer". It's structure is the following:

So if we need to print the first letter (c) and the 3rd letter (m), we do:

let word = "computer"; console.log(word[0], word[2]);

Output:

c m

Length

Length is the count of the symbols contained in a string.

It's accessed via the length function.

Example:

let word = "Hello!"; console.log(word.length);

Output:

6

Via length we can access the last symbol of a string.

Example:

let str = "The quick brown fox jumps over the lazy dog!"; console.log(str[str.length - 1]);

Output:

!

Access outside of bounds

Accessing string outside of it's bounds returns undefined value.

Let's look the following example:

let str = "Phone"; if(str[5] === undefined) { console.log("it's undefined"); }

Output:

it's undefined

The string has indexes from 0 to 4. Accessing index outside of that bound (in this case 5) returns undefined.

Contains

We can check if string is contained in a string via the includes function.

Examples:

console.log('simple'.includes('m')); console.log('simple'.includes('si')); console.log('simple'.includes('z')); console.log('simple'.includes('S'));

Output:

true true false false

String iteration

All symbols of a string can be iterated via for loop.

Let's print all letters of a word that are not vowels:

let word = 'composure'; for (let i = 0; i < word.length; i++) { let letter = word[i]; if(!'aeiou'.includes(letter)) { console.log(letter) } }

Output:

c m p s r

In this case !'aeiou'.includes(letter) means that letter is a symbol that's not a vowel letter.