JavaScript Problem Solving for Beginners

When I started learning JavaScript, I found that problem solving is the most difficult in JavaScript. Especially for beginners. Here we going to discuss some common problem solving in series in JavaScript.

Factorial

One of the most common problem solving practice that you are going to face when starting JavaScript. Factorial symbol looks like this ( ! ). What it does you pick up a number, you have to multiply that number with the all previous number. Which is something look like this:

1! = 1
2! = 1*2
3! = 1*2*3
4! = 1*2*3*4
5! = 1*2*3*4*5

So how do we do it JavaScript !

let element = 1;
for (let i = 1; i <= 10; i++) {
element = element * i;
console.log(element)
}

This is the one of the way to do factorial in JavaScript.
factorial in a recursive way.

function factorial(num) {
if (num < 0)
return -1;
else if (num == 0)
return 1;
else {
return (num * factorial(num — 1));
}
}
factorial(5);

Fibonacci

Fibonacci is a series of number, where you pick up a number from that series, and which is the result of previous two number that is added. Fibonacci series looks like this -

1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, …

Let’s see how we can do it using JavaScript

// fibonacci
let fibonacci = [0, 1];
for (let i = 2; i <= 10; i++) {
fibonacci[i] = fibonacci[i-1] + fibonacci[i-2]
}
console.log(fibonacci);

Fibonacci in a recursive way

function fibonacci(n) {
if (n == 0) {
return [0];
}
if (n == 1) {
return [0, 1];
}
else {
let fibo = fibonacci(n-1);
let element = fibo(n-1) + fibo(n-2);
fibo.push(element)
return fibo;
}
}

Swap

Swap the value of a variable, often time we need to change the value of a variable, but how do we do this? Let’s see

let a = 5
let b = 6
let x = a;
a = b
b = x;
console.log(a ,b)

there is another way which we can call the JavaScript way to do this

let x = 5;
let y = 6;
[x, y] = [y, x]

Play with Numbers

There is several way to solve and play with numbers in JavaScript
for example take a number

let num = 3.154653

If you want the number to be without decimal. Or you want to make it integer. Let’s see how we can do it

const myNum = Math.round(num);

this will give a result of 3;

well, what if we want the number to be the highest if there is a decimal. this is how we do it..

const myNum = Math.ceil(num);

Find the max value

Find the max value from different variable

const value1 = 1500;
const value2 = 900;
const value3 = 1600;
if (value1 > value2){
if (value1 > value3){
console.log(“value1 is bigger”)
}
else{
console.log(“value3 is bigger”)
}
}
else {
console.log(“value2 is bigger”)
}

Find the largest element in the array

Find the large number in the array, even in the real world sometimes you would need this.

const num = [20, 25, 48, 35, 85, 65];
let max = [0];
for (let i = 0; i < num.length; i++) {
const element = num[i];
if( element > max){
max = element;
}
}
console.log(max)

Add all the numbers in the array

const num = [20, 25, 48, 35, 85, 65];
let sum = 0;
for (let i = 0; i < num.length; i++) {
const element = num[i];
sum = sum + element;
}
console.log(sum);

Null vs. Undefined

At first glance, null and undefined may seem the same, but they are far different from each other.

null is an empty or non-existent value.

let a = null;
console.log(a);
// null

Undefined means a variable has been declared, but not defined.

let c = undefined;
console.log(c);
// undefined

Single, double, triple equal in JavaScript

= is used to declare a value

== is to compare & === is also to compare
But, there is a but

== Will look at the value and if it is similar, but not necessary in types, the result is going to be true. Al though one is number one is string.

const num = 2;
const num2 = “2”;

=== Will look at value and types as well, then the result is going to be true.

const num = 2;
const num2 = 2;

Smart way to loop in JavaScript

Using JavaScript in built methods like map, filter, find is a smarter way to loop in JavaScript, also time consuming and headache free

Map

The map() method creates a new array populated with the results of calling a provided function on every element in the calling array.

const array1 = [1, 4, 9, 16];
// pass a function to map
const map1 = array1.map(x => x * 2);
console.log(map1);
// expected output: Array [2, 8, 18, 32]

Find

The find() method returns the value of the first element in the provided array that satisfies the provided testing function.

const array1 = [5, 12, 8, 130, 44];
const found = array1.find(element => element > 10);
console.log(found);
// expected output: 12