Strings are a sequence of zero or more characters written inside quotes used to represent text.

Strings may consist of letters, numbers, symbols, words, or sentences.

Strings are immutable, they cannot be changed.

Each character in a string has an index.

The first character will be index 0 the second character will be index 1 and so on.

There are two ways to access an individual character in a string.

charAt() method

const str1 = "abc"; string

str1.charAt(0); character at index 0 → "a"

str1.charAt(1); character at index 1 → "b"

str1.charAt(2); character at index 2 → "c"

str1.charAt(3); character at index 3 → "" index not found

Alternatively use at() or slice() methods

bracket notation []

const str2 = "abc"; string

str2[0]; character at index 0 → "a"

str2[1]; character at index 1 → "b"

str2[2]; character at index 2 → "c"

str2[3]; character at index 3 → undefined index not found

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Arrays are used to store multiple values in a single variable.

Each value is called an element, and each element has a numeric position in the array, known as its index.

Arrays are zero-indexed, meaning the first element is at index 0, the second at index 1, and so on.

Arrays can contain any data type, including numbers, strings, and objects.

const arr1 = [2, 4, 6]; array

arr1[0]; element at index 0 → 2

arr1[1]; element at index 1 → 4

arr1[2]; element at index 2 → 6

arr1[3]; element at index 3 → undefined index not found

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Extract initials from a string using ↴

map() method → creates a new array from calling a function for every array element.

split() method → splits a string into an array of substrings.

charAt() method → returns the character at a specified index in a string.

toUpperCase() method → returns the value of the string converted to upper case.

join() method → returns an array as a string.

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map() method creates a new array populated with the results of calling a provided function on every element in the calling array. The original array is unchanged.

const arr2 = [5, 10, 15, 20];

arr2.map((x) => x + 10); returns ↴

[15, 20, 25, 30] → 10 added to each element

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split() method splits a string into an array of substrings based on a specified separator (delimiter). The original string is unchanged.

const str3 = "Hello"; → string

str3.split(""); returns ↴

["H", "e", "l", "l", "o"] → array

const str4 = "hello world"; → string

str4.split(" "); returns ↴

["hello", "world"] → array

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charAt() method returns the character at the given index.

If the index is out of range an empty string "" is returned.

const str5 = "hello";

str5.charAt(0); → "h"

str5.charAt(1); → "e"

str5.charAt(2); → "l"

str5.charAt(3); → "l"

str5.charAt(4); → "o"

str5.charAt(5); → "" not found

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toUpperCase() method returns a new string with all letters converted to upper case. The original string is unchanged.

const str6 = "hELlo wORLd";

str6.toUpperCase(); returns ↴

"HELLO WORLD" → uppercase

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join() method joins all elements of an array into a single string with a specified separator between each element. The original array is unchanged.

const arr4 = ["Hello", "World"]; array

arr4.join(" "); returns ↴

"Hello World" → string

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Initialize a variable to hold the string to extract initials

const string1 = "Fear of missing out"; → user input

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Define a function getInitials to extract initials from a string

function getInitials(str) {}

The function takes a string as input str and returns the capitalized first character of each word concatenated into a new string. The original string remains unchanged.

return str

Split str into an array of words.

.split(" ") split the string by spaces

map() method creates a new array by applying a callback function to each element of the array.

map(calbackFn) ↴

callback function ↴

word → current element being processed in the array

For each word, get the first character and convert it to upper case.

Join the array back into a single string without spaces.

.join("")

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Call the function with ↴

getInitials(string1);

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Extract initials from a string.