Today I will talk about some basic Javascript problems that we face regularly. Let's explain them with some simple examples.

Truthy and Falsy

You may have confused with what is true and false value in Javascript. Clear your confusion with an example:

Falsy values are= false, 0, "", ubdefined, null, NaN
Truthy values are= 1,"0"," ", {},[]

0 and “0”!? Let clear your confusion. 0 is the default false value in Javascript on the other hand “0” is a string. Every string in Javascript is true without an empty(“ ”) string.

The largest element of the array:

var nums=[1,2,3,4,5,6,7,8,9,10];
var maxNumbs= numbs[0];
for(var i=0; i<numbs.length; i++){
     var element= numbs[i];
    if(element>maxNumbs){
     maxNumbs=element
   }
}
// output 10

Count Number Of a Word:

var line= "This is Bangladesh";
var count=0;
for(var i=0; i< line.length;i++){
  var char= line[i]
  if(char==" " && line[i-1]!=" "){
     count++
    }
}
// output Bangladesh

Reverse String:

function reverseString(string){
var reverse=""
for (let i = 0; i < string.length; i++) {
var element = string[i];
reverse = element+reverse;
} 
 return reverse;
}
var sentence = "Mohammod Habib"
var result = reverseString(sentence);
console.log(result);
// output bibah dommahom

Check a Prime Number:

function IsPrimeNumber(n){
for (let i = 2; i < n; i++) {
  if(n%i==0) {
  return "Not a prime number"
  }
}
return "Prime number"
}
var number= IsPrimeNumber(13);
console.log(number)

Remove Duplicate:

var numbs =[1,2,3,4,7,5,6,7,8,9];
var uniqueNumbs=[];
for (let i = 0; i < numbs.length; i++) {
var element = numbs[i];
var index = uniqueNumbs.indexOf(element)
  if (index==-1){
  uniqueNumbs.push(element)
  }
}
console.log(uniqueNumbs)
//output uniqueNumbs=[1,2,3,4,5,6,7,8,9]

Calculate Factorial Number Using For Loop:

function factorialOf(integer) {
let factorial = 1;
for(let i = 1; i <= integer; i++) {
   factorial *= i;
  }
  return factorial;
}
console.log(factorialOf(4));

Factorial In Recursive:

function factorialOf(num) {
if(num<0){
   return -1
  }
else if(num==1){
  return 1;
 }
else{
  return(num*factorialOf(num-1));
  }
}
var result = factorialOf(5)
console.log(result)
// output 120

Fibonacci

The Fibonacci sequence starting with zero and one. The series is created by adding the previous two numbers. For example, the early part of the sequence is 0, 1, 1, 2, 3, 5, 8.

function fibonacci(num){
  var series =[0,1]
  for(var i = 2; i <= num; i++){
  series[i] = series[i-1]+series[i-2]
  }
 return series;
};
var result = fibonacci(10);
console.log(result)
//output [0,1,1,2,3,5,8,13,21,34,55]

Recursive Fibonacci:

function fibonacci(num){
  if(num==0){
  return 0;
  }
  else if(num==1){
  return 1;
  }
  else{
 return (fibonacci(num-1) + fibonacci(num-2))
  }
};
var result = fibonacci(10);
console.log(result);
// output 55