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
Calculate sum of all numbers using a for loop ↴
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
Initialize a variable to hold the array to calculate the sum of all numbers.
const array1 = [2, 4, 6, 8, 10]; → user input
Define a function findSum to calculate the sum of all numbers in an array.
function findSum(arr) {}
The function takes an array as input arr and returns the sum of all numbers in that array.
Initialize sum variable to store the total.
let sum = 0 sum
Loop through each element in the array arr
for (let x = 0; x < arr.length; x++) {}
Add the current element arr[x] to the sum
sum += arr[x]
Return the total sum.
return sum
Call the function with ↴
findSum(array1);
Calculate sum of all numbers in an array.
const array1 = [2, 4, 6, 8, 10];
function findSum(arr) {
let sum = 0;
for (let x = 0; x < arr.length; x++) {
sum += arr[x];
}
return sum;
}
call function
findSum(array1); returns ↴
30