Conditional Statements

Control flow is about the order of execution.

Conditional statements are a part of control flow, since their conditions can change the order of execution.

Let's discuss the basics of conditional statements.

---

if, if-else and if-else if

To control the flow of execution, one may wish to have different things happen based on a condition.

if is used for this purpose.

The if statement is composed of a condition and statements to run if the condition is true:

With if, one can add an else statement afterwards to execute something if the condition fails:

The syntax is:

if (condition) {
    //statements
}
else {
    //otherwise, statements
}

And lastly, one can combine and else-if into the mix for multiple conditional cases.

The syntax using else-if is:

if (condition) {
    //if statements
}
else if (condition2) {
    //else-if statements
}
else if (condition3) {
    //else-if 2 statements
}
...
[else {
    //else statements...
}];

info

When using [] around something in syntax, it means that statement/declaration is optional

Here is an example covering a mix of what we've discussed:

---

switch Statements

The statement switch is effectively another version of if else-if ... [else] chains.

The syntax of a switch case is as follows:

switch(expression) {
    case value1:
        //statements if expression matches value1
        break; 
    case value2:
        //statements if expression matches value2
        break;
    ...
    case valueN:
        //statements if expression matches valueN
        break;
    [default: 
        //statements executed when none of the values match the expression
        break; ]
}

There is an optional statement in this syntax: namely, default:

First we need to quickly cover break statements to understand a switch case:

• A break statement effectively "breaks out" of control flow.

• In the context of switch cases, calling break; forces control flow to leave the switch case.

What is default: and why is it optional?

• Regarding default: , if it is provided, something will happen whether or not a case succeeds.

  • However, if it isn't provided, then simply nothing will happen if all cases fail.

It all depends on how the user wants the program to function.

Here is an example of a basic switch case:

Here's an example with no default case being used:

---

tip

For more resources on conditional statements and control flow, visit Control Flow - MDN

---