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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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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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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Find the intersection of two arrays using ↴

Set Object → collection of unique values.

for...of loop → iterates through the values of an iterable object, such as an array, string, or map.

has() method → returns true if a specified value exists in a Set, otherwise returns false.

push() method → adds specified elements to the end of an array and returns the new length of the array.

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Set Object is a collection of unique values.

Each value can only occur once, each value is unique.

const mySet = new Set();

console.log(mySet); returns ↴

Set(0) {size: 0} → empty Set

To add values to the Set we can use the add() method.

mySet.add("a");

mySet.add("b");

mySet.add("c");

console.log(mySet); returns ↴

Set(3) {"a", "b", "c"} → values added

Try to add a duplicate value.

mySet.add("c"); character "c" is already in mySet

console.log(mySet); returns ↴

Set(3) {"a", "b", "c"} → no change

To determine if mySet has an element present we can use the has() method.

mySet.has("a"); → true

mySet.has("d"); → false

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for...of loop iterates through the values of an iterable object, such as an Array, String, Set, Map, ...

syntax

for (variable of iterable) {}

variable holds the current value of the iteration.

of keyword indicates that the loop should iterate over the values of the iterable.

iterable object that is iterable, such as an Array, String, Set, Map, ...

Iterate over each character in the string.

const str2 = "ABC";

for (const char of str2) {

console.log(char);

} returns ↴

A

B

C → printed to console

The loop will run three times, once for each character in the string.

On each iteration, the value of the current element is stored in the variable char

For each iteration of the loop, the current value of char is printed to the console.

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push() method adds new elements to the end of an array.

Add 4 to end of array.

const arr2 = [1, 2, 3];

arr2.push(4);

console.log(arr2); returns ↴

[1, 2, 3, 4] → 4 added to end of array

The push() method changes the length of the array.

arr2 is modified.

Using the spread operator creates a new array.

Add 4 to a new array.

const arr3 = [1, 2 , 3];

const arr4 = [...arr3, 4];

console.log(arr4); returns ↴

[1, 2, 3, 4] → 4 added to new array

console.log(arr3); returns ↴

[1, 2 ,3]

arr3 remains unchanged.

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Initialize the two input arrays to find their intersection.

first array ↴

const array1 = [1, 2, 3, 4]; → user input

second array ↴

const array2 = [3, 4, 5, 6]; → user input

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Define a function findIntersection() to find the intersection of two arrays.

function findIntersection(arr1, arr2) {}

The function takes two arrays as input arr1, arr2 and returns a new array with their intersection. The original arrays remain unchanged.

Each input array may contain duplicates. Duplicates will be removed inside the function.

Set constructor is used to create two new Sets from the input arrays arr1, arr2

setA = new Set(arr1) setA

setB = new Set(arr2) setB

Initialize an array to hold the intersection.

let intersection = [] intersection

for...of loop ↴

for (const element of setB) {} iterates over each element of the second Set, setB

has() method checks if current element is present in setA

!setA.has(element) if element NOT found ↴

push() method adds the element to the intersection array.

intersection.push(element)

The function returns a new array containing only the unique elements that are common in both arrays.

If there is no intersection present then an empty array [] is returned.

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Create a Set from the first array to store unique values.

const setA = new Set(arr1);

Create a Set from the second array to store unique values.

const setB = new Set(arr2);

Initialize an empty array to hold the intersection results.

let intersection = [];

Iterate over each element in the second Set and check if the current element exists in the first Set.

If condition is true, push that element to the intersection array.

for (let element of setB) {

if (setA.has(element)) {

intersection.push(element)

}

}

Return the array containing the intersection of the two arrays.

return intersection;

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Call the function with ↴

findIntersection(array1, array2);

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Find the intersection of two arrays.