Conditional Statements

In order to code decisions into our javaScript programs it's necessary to use conditional statements know as if statements.

An if statement is a
conditional statement which checks to see if a statement is true
or false and then executes some additional statements depending
on the result.

In javaScript a basic IF statement looks as follows:

if (condition) { 
    //code to be executed if condition is true 
}

A real example

//check if the statement 5 > 3 is true and if so
//then print a suitable message
    if (5 > 3){
        console.log("It is bigger!"); 
   }

We can also specify an alternative by using an else as follows:

if (5 > 3){
        console.log("It is bigger!"); 
}else {
        console.log("It is smaller");

}

The bigger than symbol > is know as a comparison operator. You may want to make use of the following operators:

We can only have 1 else with every if. If we want to specify more than one alternative then we have to use else if.

Consider the following example:

if (role == "Teacher"){

    console.log("You are a teacher!");

}

else if (role == "Student"){

    console.log("You are a student!");

}

else if (role == "Admin"){

    console.log("Your are an admin");

}

else{

     console.log("I don’t know what you are!");

}

In the above example you will notice that an else if statement is used
to specify alternative paths and that you can have more than 1 else if statement. In fact, you can have as many else if statements as you like.

Multiple conditions

You can join together different conditions with "or” or “and” statements, to test whether either statement is true, or both are true, respectively.

In JavaScript “or” is written as || and “and” is written as &&.

Say you want to test if the value of x is between 10 and 20—you could do that with a condition stating:

if(x > 10 && x < 20) {
    ...
}

If you want to make sure that country is either “England” or “Germany” you use:

if(country === 'England' || country === 'Germany') {
    ...
}

Section Exercise

Exercise 1 if

var name = "John";

if (name === "John") {

}

assert(name === "John");

Exercise 2 else

var name = "Aaron";

if (name === "John") {

} else if (name === "Aaron") {
    // Valid this condition
}

assert(name === "Aaron");

Exercise 3 multiple conditions

var name = "John";
var country = "England";
var primaryCategory, secondaryCategory;

if (name === "John" && country === "England") {
    primaryCategory = "E/J";
}
if (name === "John" || country === "England") {
    secondaryCategory = "E|J";
}

assert(primaryCategory === "E/J" && secondaryCategory === "E|J");