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
Generate a fibonacci sequence up to n terms using a while loop
while loop repeatedly executes a block of code as long as a specified condition evaluates to true.
while (condition) {
// execute code as long as condition is true
}
let x = 0; → counter
while (x < 4) {
console.log(x);
x++;
}
Initialize a counter variable x outside of the loop.
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 number of terms n to generate for a Fibonacci sequence.
const nTerms = n; → user input
Define a function fibonacci() to generate a Fibonacci sequence.
function fibonacci(num) {}
The function takes a number as input num and generates first n terms of the Fibonacci sequence.
Initialize the first two numbers of the sequence.
let num1 = 0 num1 First Fibonacci number
let num2 = 1 num2 Second Fibonacci number
Initialize a variable to hold the next Fibonacci number.
let nextNum = 0 nextNum
Start the while loop from index 2
The first two terms have already been defined.
let x = 2 x Counter to track the number of terms printed
Print the header for the Fibonacci sequence.
console.log("Fibonacci Sequence:")
Handle the case when only the first term is requested.
if (num == 1) {}
Return 0 for the first term and end execution of function.
return 0
Handle the case when only the first two terms are requested.
if (num == 2) {}
Print the first term.
console.log(0)
Return 1 for the second term and end execution of function.
return 1
For case where more than two terms are requested.
Print the first two terms - which are already defined.
console.log(num1) 0
console.log(num2) 1
Loop to calculate the next terms.
while (x < num) {}
Calculate the next term nextNum by adding the two previous numbers in the array.
nextNum = num1 + num2
Print nextNum
console.log(nextNum)
Update num1 to the previous num2
num1 = num2
Update num2 to the newly calculated nextNum
num2 = nextNum
Increment the counter by 1
x++
When the loop while (x < num) evaluates to false, the loop terminates.
Call the function with ↴
fibonacci(nTerms);
Generate the first 7 terms of the Fibonacci sequence.
num = 7
The first two terms have already been defined.
num1 = 0 first number 0
num2 = 1 second number 1
nextNum is computed by adding the two previous numbers.
nextNum = num1 + num2
let x = 2
while (x < num)
x Iteration ↴
2 num1 = 0, num2 = 1 0 + 1 → 1
3 num1 = 1, num2 = 1 1 + 1 → 2
4 num1 = 1, num2 = 2 1 + 2 → 3
5 num1 = 2, num2 = 3 2 + 3 → 5
6 num1 = 3, num2 = 5 3 + 5 → 8
First 7 terms of the Fibonacci sequence ↴
0, 1, 1, 2, 3, 5, 8
Generate the first 7 terms of the Fibonacci sequence.
const nTerms = 7;
function fibonacci(num) {
let num1 = 0;
let num2 = 1;
let nextNum = 0;
let x = 2;
console.log("Fibonacci Sequence:");
if (num == 1) {
return 0;
}
if (num == 2) {
console.log(0);
return 1;
}
console.log(num1);
console.log(num2);
while (x < num) {
nextNum = num1 + num2;
console.log(nextNum);
num1 = num2;
num2 = nextNum;
x++;
}
}
call function
fibonacci(nTerms); returns ↴
Fibonacci Sequence:
0
1
1
2
3
5
8 → printed to console