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
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
Find the maximum difference between two numbers in an array using ↴
for loop → executes a block of code a number of times.
Math.abs() static method returns the absolute value of a number.
for loop repeatedly executes a block of code until a specified condition evaluates to false.
The loop runs a block of code a set number of times, defined by an initialization, a condition, and an increment.
for (let x = 0; x < 4; x++) {
console.log(x);
}
Loop variable x is initialized to 0
Condition x < 4 is checked before each iteration.
The loop will continue to run as long as x is less than 4
The loop repeatedly executes a block of code 4 times, from 0 to 3
For each iteration of the loop, the current value of x is printed to the console.
After each iteration, x is incremented by 1 x++
When x reaches 4 the condition evaluates to false, terminating the loop.
0
1
2
3 → printed to console
Nested for loops
A nested loop is a loop inside another loop.
A nested for loop consists of an outer for loop and one or more inner for loops
Each time the outer for loop repeats, the control re-enters inside the inner for loop and starts a new execution.
The outer loop iterates through the rows, while the inner loop iterates through the columns.
const rows = [1, 2, 3];
const columns = ["A", "B", "C"];
for (let x = 0; x < rows.length; x++) {
for (let y = 0; y < columns.length; y++) {
console.log(`row ${rows[x]} : column ${columns[y]}`);
}
}
returns ↴
row 1 : column A
row 1 : column B
row 1 : column C
row 2 : column A
row 2 : column B
row 2 : column C
row 3 : column A
row 3 : column B
row 3 : column C → printed to console
Generate a multiplication table.
for (let x = 1; x <= 12; x++) {
let row = "";
for (let y = 1; y <= 10; y++) {
row += (x * y) + "\t";
}
console.log(row);
}
returns ↴
1 2 3 4 5 6 7 8 9 10
2 4 6 8 10 12 14 16 18 20
3 6 9 12 15 18 21 24 27 30
4 8 12 16 20 24 28 32 36 40
5 10 15 20 25 30 35 40 45 50
6 12 18 24 30 36 42 48 54 60
7 14 21 28 35 42 49 56 63 70
8 16 24 32 40 48 56 64 72 80
9 18 27 36 45 54 63 72 81 90
10 20 30 40 50 60 70 80 90 100
11 22 33 44 55 66 77 88 99 110
12 24 36 48 60 72 84 96 108 120 → printed to console
rows ⇣ outer loop
columns ⇢ inner loop
The outer loop iterates through the rows ⇣ 1 to 12
The inner loop iterates through the columns ⇢ 1 to 10.
Math.abs static method returns the absolute value of a number.
The method takes one argument, which is the number for which you want to find the absolute value, and it returns a positive number or zero.
Math.abs(7) → 7
Math.abs(-7) → 7
Math.abs(12.345) → 12.345
Math.abs(-12.345) → 12.345
The result is always a positive number or 0
Initialize a variable to hold the array find the maximum difference between two numbers.
const array1 = [4, 8, 6, 2, 5, 7, 9, 3]; → user input
Define a function maxDifference to find the maximum difference between two numbers.
function maxDifference(arr) {}
The function takes an array as input arr and returns the maximum number between two numbers found in the array.
Initialize a variable to store the maximum difference found.
let maxDiff = 0 maxDiff
Outer loop to iterate through each element in the array.
for (let x = 0; x < arr.length; x++) {
Inner loop to compare the current element with the following elements.
for (let y = x + 1; y < arr.length; y++) {
Calculate the absolute difference between the two elements.
const diff = Math.abs(arr[y] - arr[x]) diff
Check if the calculated difference is greater than the current maxDiff.
if (diff > maxDiff) {
If true, update maxDiff.
maxDiff = diff
Return the maximum difference found.
return maxDiff
Call the function with ↴
maxDifference(array1);
Find the maximum difference between two numbers in an array.
const array1 = [4, 8, 6, 2, 5, 7, 9, 3];
function maxDifference(arr) {
let maxDiff = 0;
for (let x = 0; x < arr.length; x++) {
for (let y = x + 1; y < arr.length; y++) {
const diff = Math.abs(arr[y] - arr[x]);
if (diff > maxDiff) {
maxDiff = diff;
}
}
}
return maxDiff;
}
call function
maxDifference(array1); returns ↴
7
9 - 2 = 7 ✔