Control Structures

Control structures are fundamental tools that allow developers to dictate how their code is executed based on conditions and logic.

We’ll explore common control structures, starting with conditional statements and loops. That too, in a lighter sense, cos over explanation can lead to confusion in this section, you should try the code on your own and figure it out by yourself based on the explanation below.

Conditional Statements

Conditional statements enable decisions in a program by branching into different paths depending on the given logical conditions.

if, else if, else

The if statement checks a condition and executes a block of code if it evaluates to true. Additional conditions can be added using else if, and a default fallback can be provided with else.

// simple if-else statement
if (condition1) {
  // Code to execute if condition1 is true
} else {
  // Code to execute if all condition1 is false
}

const age = 18;
if (age < 18) {
  console.log("Access denied: Must be 18 or older");
} else {
  console.log("Access granted");
}

// if else-if else block

if (condition1) {
  // Code to execute if condition1 is true
} else if (condition2) {
  // Code to execute if condition2 is true
} else {
  // Code to execute if all conditions are false
}

const age = 18;
if (age < 18) {
  console.log("You are a minor.");
} else if (age === 18) {
  console.log("You just became an adult!");
} else {
  console.log("You are an adult.");
}

switch statements

switch is an alternative to multiple if...else conditions and checks a value against multiple cases.

const day = "Monday";
switch (day) {
  case "Monday":
    console.log("Start of the work week!");
    break;
  case "Friday":
    console.log("End of the work week.");
    break;
  default:
    console.log("It's another day of the week.");
}

Here you can see break statement which is crucial in switch statements as it stops the execution from “falling through” to a subsequent case. You can also use return statement in place of break to stop the execution on matched key.

The default clause acts as a catch-all for any value that doesn’t match any case. It’s similar to the else in if-statements.

The following snippet shows to deal with multiple cases sharing the same code block.

switch (fruit) {
  case "apple":
  case "pear":
  case "banana":
    console.log("This is a fruit");
    break;
  case "carrot":
    console.log("This is a vegetable");
    break;
  default:
    console.log("Unknown food type");
}

Loops

Used to repeatedly execute a block of code while a condition is met or for a specified number of times.

for Loop

The for loop is great for running a block of code a specific number of times.

for (let i = 0; i < 5; i++) {
  console.log(`Iteration: ${i}`);
}

while Loops

The while loop runs while a condition is true.

let count = 0;
while (count < 3) {
  console.log(`Count: ${count}`);
  count++;
}

do...while Loops

The do...while loop guarantees the block of code executes at least once, even if the condition is false.

do {
  console.log(`Value: ${x}`);
  x--;
} while (x > 0);

Loop Control

break and continue

break

break is used to exit a loop prematurely, halting further iterations.

for (let i = 1; i <= 10; i++) {
  if (i > 5) {
    break; // Exit the loop when i > 5
  }
  console.log(i);
}

continue

continue skips the current iteration and moves on to the next one.

for (let i = 1; i <= 5; i++) {
  if (i === 3) {
    continue; // Skip iteration when i equals 3
  }

  console.log(i);
}