4.Conditionals

Conditional Statements

Conditional Statements are often used in any programming language to perform different actions based on different conditions.

The conditional statements in JavaScript are:

1. if statement.
2. if - else statement.
3. else if statement.
4. switch statement.

JavaScript if statement

In this, the part of the code will only execute if the condition given is true.

Syntax:

if (condition) {
    // code to be executed if the condition satisfies
}

Example:

var a = 10;
if (a<=15) { // condition is true(10<=15)
    console.log("Value of a is less than 15");
}

Output:

Value of a is less than 15

Flowchart:

JavaScript if-else statement

In this, if the given condition satisfies the part of code under if will get executes otherwise the code under else will get execute.

Syntax:

if (condition) {
    // code get executes if the condition is true
} else {
    // this will get execute if the condition is false
}

Example: An example program to check whether the citizen is adult or not.

var age = 26;
if (age>=18) {
    console.log("Citizen is Adult");
} else {
    console.log("Citizen is not Adult");
}

Output:

Citizen is Adult

Explanation:

Here the age is 26 that means the citizen is Adult so the code under if gets executed as the condition is true.

Flowchart:

JavaScript if - else if statement

In this, if the conditions of if and else if is satisfied the code under if and else if then the code under these if and else if will get executes, otherwise the code under else will get executes.

Syntax:

if (condition 1) {
    // will execute if the condition is true
} else if (condition 2) {
    // will executes if condition 2 is true
} else {
    // will execute if the condition is false
}

Example:

var a = 100;
if (a==10) {
    console.log("Value of a is equal to 10");
} else if (a==50) {
    console.log("Value of a is equal to 50);
} else {
    console.log("Value of a is not equal to 10 or 50");
}

Output:

Value of a is not equal to 10 or 50

Explanation: Here the value of a is 100 and none of the conditions given is satisfied so the code under else gets executed.

JavaScript switch statement

In this, one of the case(condition) gets executed among multiple cases(conditions).

It is similar to if - else if statement and in switch you can use numbers and characters. You will get clear with an example below.

Syntax:

switch (condtion) {
    case 1:
    // gets executes if condition satisfies
    break;

    case 2:
    // gets executes if condition satisfies
    break;

    case 3:
    // gets executes if condition satisfies
    break;

    default:
    //gets executes if none of the cases gets matched with the condition
}

Example:

var res = 9.0;
var grade;

switch (res) {
    case 9.0:
    grade = 'A';
    break;

    case 8.0:
    grade = 'B';
    break;

    case 7.0:
    grade = 'C';
    break;

    default:
    grade = 'F';
}
console.log(grade);

Output:

A

Explanation:

Here, the value of res is 9.0 so the case 9.0 is executed. And if the grade is not matching with any of the cases then the code default gets executed.

JavaScript Ternary Operator

You can also use ternary operator instead of if - else .

Syntax:

(condition)? statement-1 : statement-2;

If the condition is true then statement-1 will get executed, else the statement-2 will get executed.

Example:

var marks = 80;
var result = (marks>=35)? "Pass" : "Fail";
console.log(result);

Output:

Pass

Conclusion

Congratulations! You've successfully learnt about JavaScript conditional statements.

Keep exploring JavaScript 👋

Contributor : Abhinandan Adhikari ❤️