Mastering Loop Control: Break and Continue in TypeScript | CodeSignal Learn

Mastering Loop Control: Break and Continue in TypeScript | CodeSignal Learn

Introduction and Lesson Overview

Are you prepared to dive into the deep end of TypeScript ? Our expedition today will revolve around comprehending two essential instructions: the break and continue commands. The break command, in its simplest terms, stops a looping structure dead in its tracks, disregarding its original condition. On the other hand, the continue command bypasses the remaining loop iteration and immediately proceeds to the following one. We'll get our hands dirty by understanding these commands using simple for and while loops, before exploring the intricacies of nested loops.

Directing Single 'for' Loop Control — The Break Statement

Recall the for loop? Well, its iterations continue as long as the set condition is met. In this section, our agenda is to introduce and understand the concept of break . Once this command is encountered, the loop abruptly stops, without any hesitation! Let's imagine a game of hide-and-seek, where every hiding spot corresponds to an iteration of the loop. The game ends when the hidden object (break) is found. Here's how it translates to TypeScript: TypeScript for (let i = 0; i <= 10; i++) {if (i === 5) {console.log(`Hidden object found at position ${i}`); // Our hidden object is at position 5 break; // STOP! We found the object. No need to search further.} console.log(`No hidden object at position:${i}`);} /* Prints: No hidden object at position: 0 No hidden object at position: 1 No hidden object at position: 2 No hidden object at position: 3 No hidden object at position: 4 Hidden object found at position 5 */ Notice how the set of numbers from 0 to 10 couldn't execute fully due to the break at i = 5, terminating the subsequent iterations prematurely.

Directing Single 'for' Loop Control — The Continue Statement

Now, the continue command skips the current iteration and swiftly moves onto the next one. Picture this as picking candies from a jar while deciding to skip a specific candy. That's the essence of the continue command. TypeScript for (let i = 0; i < 10; i++) {if (i === 5) { // Position 5 has the candy we're avoiding continue; // SKIP! No candy for me, thank you. On to the next candy!} console.log(`Picked candy at position: ${i}`);} /* Prints: Picked candy at position: 0 Picked candy at position: 1 Picked candy at position: 2 Picked candy at position: 3 Picked candy at position: 4 Picked candy at position: 6 Picked candy at position: 7 Picked candy at position: 8 Picked candy at position: 9 */ Observe how the continue statement effectively omits i = 5, and the loop covers all values from 0 to 9 .

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Managing Single 'while' Loop Control — Break and Continue

The commands break and continue function in while loops similarly to their behavior in for loops. Imagine scrolling through a playlist, but deciding to skip song number 5: let song = 0; while (song < 10) {song++; if (song === 5) { // We are at song number 5 continue; // SKIP! Let's move on to the next song.} console.log(`Playing song number: ${song}`);} /* Prints: Playing song number: 1 Playing song number: 2 Playing song number: 3 Playing song number: 4 Playing song number: 6 Playing song number: 7 Playing song number: 8 Playing song number: 9 Playing song number: 10 */ Now, let's imagine we're flipping through a photo album and wish to stop at a particular picture: let photo = 0; while (photo < 100) {photo++; if (photo === 23) { // Found our preferred photo console.log(`Found the photo at position: ${photo}`); break; // STOP! We've found the photo. No need to keep searching.}} // Prints: Found the photo at position: 23

TypeScript

let song = 0;

while (song < 10) {
  song++;
  if (song === 5) { // We are at song number 5
    continue; // SKIP! Let's move on to the next song.
  }
  console.log(`Playing song number: ${song}`);
}

/*
Prints:
Playing song number: 1
Playing song number: 2
Playing song number: 3
Playing song number: 4
Playing song number: 6
Playing song number: 7
Playing song number: 8
Playing song number: 9
Playing song number: 10
*/

TypeScript

let photo = 0;

while (photo < 100) {
  photo++;
  if (photo === 23) { // Found our preferred photo
    console.log(`Found the photo at position: ${photo}`);
    break; // STOP! We've found the photo. No need to keep searching.
  }
}

// Prints: Found the photo at position: 23

Remember playing with nested puzzle boxes? The break command allows us to conclude the nested loop operation once the puzzle is solved:

TypeScript

for (let outerBox = 0; outerBox < 3; outerBox++) {
  for (let innerBox = 0; innerBox < 3; innerBox++) {
    if (outerBox === 1 && innerBox === 1) { // The puzzle solution is inside the inner box of the outer box.
      console.log(`Puzzle was inside outer box ${outerBox} and inner box ${innerBox}`);
      break; // STOP! We've solved the puzzle. No need to open more boxes.
    }
    console.log(`Puzzling at outer box ${outerBox} and inner box ${innerBox}`);
  }
}

It's important to note that the break command exclusively ends the inner loop, and the outer loop continues its execution. Since the puzzle is solved we'd technically want to end both loops but that's a topic for another lesson.