Loops in JavaScript are used to execute a block of code multiple times until a specific condition is met. This prevents repetition and makes the code more efficient.
for LoopThe for loop is used when the number of iterations is known in advance.
for (initialization; condition; increment/decrement) {
// Code to execute
}
for (let i = 1; i <= 5; i++) {
console.log("Iteration:", i);
}
📌 This loop runs 5 times, increasing i from 1 to 5.
while LoopThe while loop executes a block of code as long as the condition is true.
let i = 1;
while (i <= 5) {
console.log("Iteration:", i);
i++;
}
📌 This runs while i is ≤ 5, incrementing i in each loop.
do...while LoopThe do...while loop executes the code at least once, then continues while the condition is true.
let i = 1;
do {
console.log("Iteration:", i);
i++;
} while (i <= 5);
📌 This loop executes once, even if the condition is false initially.
for...in Loop (Used for Objects)The for...in loop iterates over the properties (keys) of an object.
let student = { name: "John", age: 21, grade: "A" };
for (let key in student) {
console.log(key + ": " + student[key]);
}
📌 This prints each key-value pair from the object.
for...of Loop (Used for Arrays)The for...of loop iterates over the values of an array.
let numbers = [10, 20, 30, 40];
for (let num of numbers) {
console.log(num);
}
📌 This prints each element in the array.
break Statementfor (let i = 1; i <= 5; i++) {
if (i === 3) break;
console.log(i);
}
// Output: 1, 2
📌 Loop stops when i === 3.
continue StatementSkips the current iteration and moves to the next one.
for (let i = 1; i <= 5; i++) {
if (i === 3) continue;
console.log(i);
}
// Output: 1, 2, 4, 5
📌 The loop skips i = 3 but continues with the next numbers.
for → When iterations are known.while → When condition controls execution.do...while → Executes at least once.for...in → Loops over object properties.for...of → Loops over array values.break & continue control loop flow.