Chapter 7 Cheatsheet: Loops

This cheatsheet summarizes the iteration and looping mechanics covered in Chapter 7. Use it as a quick reference when dealing with repeated code execution.

Standard for Loops

The classic C-style loop, ideal for executing logic a specific, known number of times using a counter variable.

// for (initialization; condition; increment)
for (let i = 0; i < 5; i++) {
  console.log(i); // 0, 1, 2, 3, 4
}

while Loops

Ideal for scenarios where you do not know the exact number of iterations beforehand, such as traversing a linked list or waiting for a specific threshold. Runs endlessly as long as the condition evaluates to true.

let balance = 100;
while (balance > 0) {
  balance -= 10;
}

Loop Control Keywords

break Immediately terminates the loop and escapes entirely. Required to safely escape an infinite loop.

for (let i = 0; ; i++) {
  if (i === 10) break; // Exits at 10
}

continue Immediately skips the remainder of the current iteration and proceeds to the next cycle of the loop.

for (let i = 0; i < 5; i++) {
  if (i === 2) continue; // Skips 2
  console.log(i); // 0, 1, 3, 4
}

for...in Loops

Used strictly for iterating over the string keys (properties) of an Object. Use bracket notation obj[key] to dynamically retrieve the associated value.

const settings = { theme: "dark", notifications: true };

for (const key in settings) {
  console.log(key, settings[key]);
}
// "theme dark"
// "notifications true"