What types of for loops do you know in JavaScript?

In JavaScript, there are several types of for loops:

• for (classic): Used for iterating over a range of numbers or executing a block a certain number of times.

  // Iterating over a range of numbers
  for (let i = 0; i < 5; i++) {
    console.log(i); // 0, 1, 2, 3, 4
  }
  

• for...in: Iterates over the keys (properties) of an object, including properties in its prototype chain. Not recommended for array iteration due to potential issues with order and non-numeric properties.

  const obj = { a: 1, b: 2, c: 3 };
  for (const key in obj) {
    console.log(`${key}: ${obj[key]}`);
    // a: 1
    // b: 2
    // c: 3
  }
  
  const arr = ['apple', 'banana', 'orange'];
  for (const index in arr) {
    console.log(index); // 0, 1, 2 (keys are indices in this case)
  }
  

• for...of: Iterates over the values of iterable objects such as arrays, strings, Map, Set, TypedArray, and arguments. Recommended for array iteration.

  const arr = ['apple', 'banana', 'orange'];
  for (const element of arr) {
    console.log(element);
    // apple
    // banana
    // orange
  }
  
  const str = "hello";
  for (const char of str) {
    console.log(char);
    // h
    // e
    // l
    // l
    // o
  }
  

Comparison table:

Loop	Purpose	Iterated elements	Recommended for
for	Iterating over a numeric range, repeating	A specific number of times	General loops
for...in	Iterating over keys (properties) of objects	Keys (properties)	Objects
for...of	Iterating over values of iterable objects	Values	Arrays, strings, Map, Set