Control flow is the order in which individual statements, instructions, or function calls are executed within a script. JavaScript features various control flow structures including: conditions (if, else, else if), loops (for, while), and exceptions.

Conditions in JavaScript

A condition is a mechanism of decision-making in JavaScript. 'if' statement is used to specify a block of code to be executed if a condition is true. 'else' statement is used to specify a block of code to be executed if the same condition is false. 'else if' statement is used to specify a new condition to test if the first condition is false.

if (condition) {
  // block of code to be executed if the condition is true
} else if (anotherCondition) {
  // block of code to be executed if the condition is false and 'anotherCondition' is true
} else {
  // block of code to be executed if the condition is false and 'anotherCondition' is also false
}

Loops in JavaScript

A loop is a sequence of instructions that is continually repeated until a certain condition is reached. A 'for' loop repeats until a specified condition evaluates to false. The JavaScript 'for' loop is much more flexible than it is in most other languages, supporting both traditional styles of use and other, JavaScript-specific ones. The 'while' loop executes a block of code as long as a specified condition is true.

for (let i = 0; i < 10; i++) {
  console.log(i);
}

let i = 0;
while (i < 10) {
  console.log(i);
  i++;
}

Exceptions in JavaScript

An exception is an unusual condition requiring special handling. In JavaScript, we use 'try', 'catch', and 'finally' statements to implement exception handling. When an exception is thrown in the 'try' block, the exception is caught and handled in the 'catch' block. And the 'finally' block is used to execute code regardless of the result of the try...catch block.

try {
  // trying to execute some code
} catch (error) {
  // handling error if above block fails
  console.log(error);
} finally {
  // code to be executed regardless of the try / catch result
}

Just like how you decide whether to have cereal or pancakes for breakfast, computers also have to make decisions. Control flow in JavaScript is like the computer's recipe for making those decisions. It helps the computer decide what to do next.

If Statements in JavaScript

Think about when your mommy and daddy say, 'If you finish your vegetables, then you can have dessert'. In the computer's language, JavaScript, this is called an 'if statement'. The computer checks if something is true (like you finishing your vegetables), and if it's true, it does a certain thing (like giving you dessert).

if (youAteYourVegetables) {
   giveDessert();
}

Else Statements in JavaScript

What happens if you don't finish your vegetables? Maybe you won't get dessert. That's the 'else' part. In JavaScript, it's written as 'else'. It tells the computer what to do if the first thing it checked (like you eating your vegetables) isn't true.

if (youAteYourVegetables) {
   giveDessert();
} else {
   noDessert();
}

For Loops in JavaScript

Imagine you're putting away your toys. You do the same thing for each toy: pick it up and put it in the toy box. In JavaScript, this is called a 'for loop'. It tells the computer to do the same thing over and over (like pick up a toy and put it in the box) until something tells it to stop (like when there are no more toys).

for (let toy of toys) {
   putInToyBox(toy);
}

While Loops in JavaScript

A 'while loop' is like playing a game of tag. You keep running 'while' you're still 'It'. In JavaScript, we can tell the computer to keep doing a task 'while' a certain condition is true.

while (youAreIt) {
   keepRunning();
}