Control Statement & Loop

If...Else

The if statement executes a statement if a specified condition if truthy.
If the condition is falsy, another statement can be executed.

                  
var tomr = 'rain';
if(tomr == 'rain')
{
    console.log('Take a raincoat');
} else {
    console.log('No need to take a raincoat');
}

Challenge

Write a program that works out whether if a given year is a leap year or not?

                       
                       
var year = 2004;
if(year % 4 === 0){
    if(year % 100 === 0){
        if(year % 400 === 0){
            console.log('Leap year');
        } else {
            console.log('Not a leap year');
        }
    }
    else {
        console.log('Leap year');
    }
} else {
    console.log('Not a leap year');
}

What is truthy and falsy values in JavaScript?

We are total 5 falsy values in JavaSciprt:
1. 0
2. ""
3. undefined
4. null
5. NaN

                       
if(score = 0) { // we are comparing, we are assigning and 0 is false.
    console.log("OMG, we loss the game");
} else {
    console.log("OMG, we won the game");
}

Conditional (ternary) operator

The conditional (ternary) operator is the only JavaScript operator that takes three operands.

                                      
variableName = (condition) ? value1:value2

                   
var age = 16;
console.log((age >= 18) ? "You can vote" : "You can't vote");

Switch Statement

Evaluates an expression, matching the expression's value to a case clause, and executes statements associated with that case.

1_st without using switch find the area of circle, triangle and rectangle.

                   
var shape = 'circle'

if(area == "circle"){
        console.log("the area of the circle is : " + PI*r**2);
}else if(area == "triangle"){
        console.log("the area of the triangle is : " + (l*b)/2);
}else if(area == "rectangle"){
        console.log("the area of the rectangle is : " + (l*b));
}else{
        console.log("please enter valid shape");
}

Using switch case

                   
var shape = 'circle' ;
var PI = 3.142, l=5, b=4, r=3;

switch(shape){
    case 'circle': 
    console.log("the area of the circle is : " + PI*r**2);
    break;

    case 'triangle':
    console.log("the area of the triangle is : " + (l*b)/2);
    break;

    case 'rectangle':
    console.log("the area of the rectangle is : " + (l*b));
    break;

    default:
    console.log("please enter valid shape");
}

Break and continue

Break terminates the current loop, switch, or lobel statement and transfers program control to the statement following the terminated statement.
Continue terminates execution of the statements in the current iteration of the current or labeled loop, and continues execution of the loop with the next iteration.

Loops

While loop statement

The while statement creates a loop that executes a specified statement as long as the test condition evaluates to true.

                                  
var num = 20;
while(num <= 10) {
    console.log(num); // infinite loop
    num++;
    // num--;
}

Do-While Loop statement

                    
var num = 5;
do {
    console.log(num); 
    num++;
} while (num <= 10)

For Loop

                                  
for(var num = 0; num <= 10; num++)
{
    console.log(num);
}

Challenge Time

JavaScript program to print table for a given number (8)?

                       
var tableof = 8
for(var i = 1; i <= 10; i++) {
    console.log(tableof + " * " + i + " = " + tableof * i);
}

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