The while loop is a type of loop statement in JavaScript that allows you to repeatedly execute a block of code as long as a specified condition is true.
The basic syntax of a while loop in ECMAScript 2021 is as follows:
while (condition) {
// code to be executed
}
Here, condition is the expression that is tested before each iteration of the loop. As long as it returns a truthy value, the loop will continue to execute the block of code inside the loop.
Here are some examples of using while loop in JavaScript:
Example 1: Displaying numbers from 1 to 5 using while loop
let i = 1;
while (i <= 5) {
console.log(i);
i++;
}
1
2
3
4
5
Example 2: Reversing a string using while loop
let str = "hello";
let reversedString = "";
let i = str.length - 1;
while (i >= 0) {
reversedString += str[i];
i--;
}
console.log(reversedString);
Output:
olleh
Example 3: Calculating the factorial of a number using while loop
function factorial(n) {
let result = 1;
let i = n;
while (i > 0) {
result *= i;
i--;
}
return result;
}
console.log(factorial(5)); // Output: 120
In this example, we define a factorial function that takes a number n as input and calculates its factorial using a while loop. The loop keeps multiplying the result variable by i, decreasing its value by 1 at each iteration until i reaches 1. The final value of result is returned as the factorial of n.
These are just a few examples of how you can use the while loop in JavaScript. You can use it to perform a wide range of tasks, such as iterating over arrays, fetching data from APIs, implementing game loops, and more.