Control Flow

Conditionals

Conditionals allow programmers to perform certain tasks when a particular condition is met. They are a fundamental part of most programming languages. Conditionals are a usually implemented through an if…else… structure. They control behavior and determine whether or not some pieces of code should run.

For example, in JavaScript,

if (hour < 12) {
    greeting = "Good Morning"
} else if (hour < 17) {
    greeting = "Good Afternoon"
} else {
    greeting = "Good Evening"
}

Loops

Loops tell the computer to perform a certain task repeatedly, a certain number of times or until a condition is met. Very often when you write code, you want the same block of code to run over and over again in a row. Instead of adding several almost equal lines in a script we can use loops to perform a task like this.

There are two different kinds of loops in JavaScript,

for - loops through a block of code a specified number of times

for (let v = start; v <= end; v += increment) {
        // code that is run multiple times.
}

To control the behaviour of the for loop we use an increment variable, in this case it’s ‘v’. while - loops through a block of code while a specified condition is true.

while (v <= end_value) {
    // code that is executed until the above condition in met
    // Common Mistake: If you don't change the value of v in here, you will have an infinite loop!
    // Make sure you avoid doing that since it can be difficult to find the issue (debug) as a beginner.
}

The *do…while…* loop is variant of the while loop, it contains a block of code that is executed once, then a while loop is executed.,

do {
   // code that is executed once
} while (v <= end_value) {
   // code that is executed multiple times.
}

There are still other variation of loops such as the ‘for…in…’ loop, but they all follow the same basic principles.