8-loops

🔁 2. Loops in JavaScript

Definition:

Loops are used to execute a block of code repeatedly as long as a specified condition is true. Loops are essential for processing arrays, handling asynchronous logic, and iterating over data in MERN stack apps.

---

a. for Loop

Syntax:

for (initialization; condition; increment) {
  // code block
}

Example:

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

---

b. while Loop

Syntax:

while (condition) {
  // block of code
}

Example:

let i = 0;
while (i < 5) {
  console.log(i);
  i++;
}

---

c. do...while Loop

Executes the block at least once, even if the condition is false.

Syntax:

do {
  // block
} while (condition);

Example:

let i = 0;
do {
  console.log(i);
  i++;
} while (i < 3);

---

d. for...in Loop

Used to iterate over the properties of an object.

Syntax:

for (let key in object) {
  // code
}

Example:

let user = { name: "John", age: 30 };
for (let key in user) {
  console.log(key + ": " + user[key]);
}

---

e. for...of Loop (ES6)

Used to iterate over iterable objects like arrays, strings, etc.

Syntax:

for (let value of iterable) {
  // code
}

Example:

let fruits = ["apple", "banana"];
for (let fruit of fruits) {
  console.log(fruit);
}

---

f. break and continue

• break: Exits the loop immediately.

• continue: Skips the current iteration and continues the loop.

Example:

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

---