# Javascript Problem Solving

# What is Problem Solving?

Problem-solving in programming is identifying a solution and steps / Techniques to solve the problem.

In this blog, we will solve five fundamental problems using Javascript.

# Problem 1: Find a Factorial of a number

## Problem Algorithm:

We need to find the factorial of the number, for example, let’s find the factorial for the number 5! = 5 x 4 x 3 x 2 x 1 = 120. Therefore, the factorial for the number 5 is 120.

**Step 1:** Start the Program.

**Step 2:** Declare the variable(num) to store the input value for which factorial needs to be found.

**Step 3:** Declare another variable(factorial) to store the factorial output value.

**Step 4:** now store the num value in the factorial variable at first.

**Step 5:** Give iteration using a while loop with condition (i.e., num value is greater than 1).

**Step 6:** if the num value is greater than 1 it will come into the while loop.

**Step 7:** num value is decremented.

**Step 8:** Multiply factorial and num values and store them in the factorial variable.

**Step 9:** Repeat step 6 and step 7, until the condition gets failed(i.e., num value is greater than 1).

**Step 10:** when the num value is equal to 1, the condition gets failed and it will come out of the loop and returns the output, which is the factorial value.

**Step 11:** End the program.

## Program Code:
```
var num=5;
factorial=num;
while(num>1){
    num--;
    factorial=factorial*num;
}
console.log(factorial);  //120
```
# Problem 2: Fibonacci Series of first 10 numbers

# Problem Algorithm:

**Step 1:** Start the Program.

Step 2: Declare the num variable and it holds the series of values till which we going to generate the Fibonacci series.

**Step 3:** Declare two variables named firstNo and secondNo and store 0 in firstNo and 1 in secondNo.

**Step 4:** for loop is used to iterate through the loop and generate the Fibonacci series and it is given with the condition to check if i is less than the num value.

**Step 5: **if the condition is satisfied it will execute the statements inside the for loop.

**Step 6: **print the firstNo value.

**Step 7:** add firstNo and secondNo values and store them in the thirdNo variable.

**Step 8:** swap the firstNo with the secondNo.

**Step 9: **swap the secondNo with the thirdNo.

**Step 10:** Repeat Step 6 to Step 9, until the condition gets fails.

**Step 11:** End the program.

# Problem Code:
```
var num=10;
firstNo=0;
secondNo=1;
for(i=0;i<num;i++){
    console.log(firstNo);
    thirdNo=firstNo + secondNo;
    firstNo=secondNo;
    secondNo=thirdNo;
} 
Output
0
1
1
2
3
5
8
13
21
34
```

# Problem 3: Reverse a string

In Javascript, to reverse a string we have a method called reverse()

## Problem Algorithm:      

**Step 1: **Start the program.

**Step 2:** declare the variable str and store the string which needs to be reversed.

**Step 3:** Using the split() method we will split the string into an array of characters and store it in the variable named array.

**Step 4:** Next, step we will use the reverse() method to reverse the array elements which are stored in the array variable.

**Step 5:** We will convert array elements into string characters using the join() method and print the output.

**Step 6: **End the Program.

## Problem Code:
```
var str='hello programmers';
var array=str.split('');
var rev_arr=array.reverse();
var join_str=rev_arr.join('');
console.log(join_str); // sremmargorp olleh
```


# Problem 4: Return the number of vowels in a string

# Problem Algorithm:

**Step 1:** Start the Program.

**Step 2:** declare the variable str to store the string characters.

**Step 3:** next declare the count variable to store the count of vowels in the string after performing the match() method and the length property and print the output.

**Step 4:** End the program.

## Problem Code:

```
var str='hello programmers';
var count=str.match(/[aeiou]/gi).length;
console.log(count);
```
Here, we are using the match() method. Match() method is used to match the characters given inside it and the length property will calculate the length of characters it matched. 

# Problem 5: sum of numbers within an array

# Problem Algorithm:

**Step 1:** Start the program.

**Step 2: **Declare a variable named arr to store array elements.

**Step 3:** Declare a variable sum with the value of 0.

**Step 4:** for loop is used to iterate through the array of elements until the condition gets failed and print the output.

**Step 5:** End the Program.

## Problem Code:
```
var arr=[1,2,3,4,5];
var sum=0;
for(i=0;i<arr.length;i++){
    var sum = sum+arr[i];
}
console.log(sum); //15
```

In the next blog, we will explore arrays in detail.