we use conditional statement in javascript when we want to perform different actions based on different conditions. They are the fundamental part of programming and use when certain conditions are either true or false. uderstanding them will enable you to use them effectively and allows you to execute specific blocks of code based on conditions.

The main type of conditional statement in Javascript are;

1. If statement
2. If else Statement.
3. If else, if else statement (else if).
4. Switch statement.
5. Tenary operator (Conditional Operator)

The If statement

The if statement in javascript is the most basic type of expression. it is a statement that always returns true, when an expression is false it will not evalutae the expression, it will only be executed when it is true.

const samuelAge = 18;
const felixAge = 12;

if (samuelAge > felixAge) {
       console.log("Samuel is the eldest brother of Felix");
} 

// output Samuel is the eldest brother of Felix\

The output here will be Samuel is the eldest brother of felix, because the conditions evaluate to be true. However when the statement is false the code will not run.

const felixAge = 12;
const samuelAge = 18;

if (felixAge > SamuelAge) {
  console.log("Felix is older than Samuel");
}

// output: no output because it is false

This code will have no output, since felixAge is less than (<) samuelAge. This will evaluate to false and will be ignored because it is not a truthy statement.
The if keywords is used to create an if statement, which is then followed by a condition enclosed in parenthesis and the code to be executed enclosed in curly brackets. it may be expressed simply as if () {}.

If else Statement

if else statement is applicable when we want the conditions to be either true or false. when we want something to occur in the event that the condition is not fulfilled i.e. false then we use if else statement. the if statement comes first and the else statement comes follows and has no condition in parathesis.

const felixAge = 12;
const samuelAge = 18;

if (felixAge > samuelAge) {
       console.log("Samuel is the eldest brother of Felix");
} else {
console.log("Felix is the eldest brother of Samuel");
}

//output: Felix is the eldest brother of Samuel

This statement above is false!!! when executing an if statement they are always true but when the if statement are not true the codes moves on to the else statement and execute the statement that is false. The condition is false because felix is not older than samuel.

If else if else (The else if Statement)

If else statement is nested to create an else if clause. it is often use for conditions that are true or false. The else if statement can evaluate multiple possibe outcomes or options with different block of code in a single decision-making structure.

let cgpa = 4.5 

if (cgpa >= 4.5) {
console.log("First Class")
} else if (cgpa >= 3.5) {
  console.log("Second Class Upper")
} else if (cgpa >= 2.4) {
console.log("Second Class Lower")
} else if (cgpa >= 1.5) {
console.log("Third Class")
} else {
console.log("pass")
}

// output: First class

we can have so many else if statemets as necessary but then in the case of many else if statement, the switch statement can be preferred for readability, understandability, and clarity in the looks of code.

The Switch Statement

let firstClassCgpa = 4.5 

function cgpaClassification (cgpa) {
switch(true) {
case cgpa >= 4.5:
console.log ("congratulations you have archived a first class");
break;
case cgpa >= 3.5:
console.log ("well done you have archived a second class upper");
break;
case cgpa >= 2.4:
console.log ("second class lower");
break;
case  cgpa >= 1.5:
console.log("Third Class");
break;
default:
console.log("pass");
   }
}

cgpaClassification(firstClassCgpa)

// output: congratulations you have archived a first class

The case keyword is where the expression will be defined regarding the block of code to be executed, The break keyword in the switch statement indicates that javascript should stop the execution inside the switch block when the match case is valid, if there is no break keyword the execution will continue to the next case or default. The default shows that if it does not match any of the expression, the particular code define under the default should execute.

Conditional (Ternary) operator

This actually operate in the same way as if else statement in a simpler version just that it is written in another way or shorter form. it involve a questions mark "?" which indicate that it is true and a semi-colon ":" for false. it reduce the amount of code and make the code more readable to comprehend when dealing with simple conditions.

let samuelAge = 18 
const eligibility = (samuelAge >=18) ? "you are eligible to vote" : "you are not eligible to vote"

//output: you are eligible to vote

Inconclusion, conditional statement is well used in javascript to determine output of our programs based on certain conditions, and it is found in most programming language. however knowing how to use if statement, if else statement, else if statement, switch statement, and ternary operator will determine our programming output and it will go a long way.