1. For Loop:

The for loop is a versatile and widely used construct in JavaScript. It allows you to execute a block of code repeatedly for a specified number of times. The basic syntax is as follows:

for (initialization; condition; iteration) {
// code to be executed
}

The initialization is executed only once at the beginning, the condition is checked before each iteration, and the iteration is performed after each iteration.

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

2. While Loop:

The while loop is used when the number of iterations is not known beforehand, and it continues executing the block of code as long as the specified condition is true.

while (condition) {
// code to be executed
}

Be cautious with while loops to avoid infinite loops by ensuring that the condition eventually becomes false.

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

3. Do-While Loop:

Similar to the while loop, the do-while loop executes the block of code at least once before checking the condition. This is useful when you want to guarantee the execution of the code inside the loop at least once.

do {
// code to be executed
} while (condition);

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

4. For…in Loop:

The for…in loop is used to iterate over the enumerable properties of an object. It is important to note that this loop should not be used for iterating over arrays, as it may not produce the expected results.

for (let property in object) {
// code to be executed
}
Examples:
let person = {
name: 'John',
age: 30,
occupation: 'developer'
};

for (let key in person) {
console.log(key + ': ' + person[key]);
}