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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Numbers are used to represent both integer and floating-point values.

Numbers are most commonly expressed in literal forms like 255 or 3.14159 ↴

let num1 = 5; → number

let num2 = 2.5; → number

let num3 = num1 + num2;

console.log(num3); returns ↴

7.5 → number

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Convert string to camel case using ↴

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

trim() method → removes whitespace from both ends of the string and returns a new string, without modifying the original string.

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

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

slice() method → extracts a part of a string and returns it as a new string, without modifying the original string.

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

toLowerCase() method → returns the value of the string converted to lower case.

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

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trim() method removes whitespace from both ends of a string and returns a new string, without modifying the original string.

const str3 = " Hello World "; → string with leading and trailing whitespace

str3.trim(); returns ↴

"Hello World" → string without whitespace

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toLowerCase() method converts all letters to lower case. The original string is unchanged.

const str4 = "hELlo wORLd";

str4.toLowerCase(); returns ↴

"hello world" → lower case

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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 str5 = "Hello"; → string

str5.split(""); returns ↴

["H", "e", "l", "l", "o"] → array

const str6 = "hello world"; → string

str6.split(" "); returns ↴

["hello", "world"] → array

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

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

const str7 = "hello";

str7.charAt(0); → "h" first character

str7.charAt(1); → "e"

str7.charAt(2); → "l"

str7.charAt(3); → "l"

str7.charAt(4); → "o"

str7.charAt(5); → "" not found

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toUpperCase() method converts all letters to upper case. The original string is unchanged.

const str8 = "hELlo wORLd";

str8.toUpperCase(); returns ↴

"HELLO WORLD" → upper case

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slice() method extracts a part of a string and returns it as a new string, without modifying the original string.

syntax ↴

slice(start) return a new string from start index to end of string

slice(start, end) return a string from start index to end index of string (exclusive).

Return a new string from index 1 to end of string.

const str9 = "Hello World";

str9.slice(1); start index is 1

returns ↴

"ello World"

Return a new string from index 1 to index 9 (exclusive).

const str10 = "Hello World";

str10.slice(1, 9); start index is 1 end index is 9 (not included)

returns ↴

"ello Wor"

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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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To capitalize a word

Convert entire string to lower case.

Capitalize first character.

Concatenate with the rest of the string.

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Initialize a variable to hold the string to tranform to camel case.

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Define a function toCamelCase to tranform a string into camel case.

function toCamelCase(str) {}

The function takes a string as input str and returns a new string that is transformed into camel case. The original string remains unchanged.

Trim whitespace from both ends of the string str

str.trim()

Convert the string to lower case.

.toLowerCase()

Split the string into an array of words.

.split(" ") → returns an array

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

map(calbackFn) ↴

After the first word, capitalize the first letter of subsequent words and concatenate with the rest of the word.

Join the array back into a single string without spaces.

.join("")

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Call the function with ↴

toCamelCase(string1);

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Convert string to camel case.

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Alternative using a ternary operator ↴