TypeScript while Loop

Introduction

In this chapter, we will explore the while loop in TypeScript. The while loop is a control flow statement that allows you to execute a block of code as long as a specified condition is true. Understanding how to use the while loop is essential for managing loops that require condition-based repetition in TypeScript programs.

Table of Contents

• Definition
• While Loop Syntax
• Basic While Loop
• Do-While Loop
• Nested While Loop
• Complete Example with Output
• Conclusion

Definition

The while loop repeats a block of code as long as a specified condition is true. It is useful when the number of iterations is not known before entering the loop.

While Loop Syntax

Syntax

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

Example

This example demonstrates a basic while loop that prints numbers from 0 to 4.

let i: number = 0;

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

Output

0
1
2
3
4

Basic While Loop

The basic while loop continues to execute the block of code as long as the specified condition remains true.

Example

This example prints the first five odd numbers using a while loop.

let num: number = 1;

while (num < 10) {
  console.log(num);
  num += 2;
}

Output

1
3
5
7
9

Do-While Loop

The do-while loop is similar to the while loop, but it guarantees that the code block will be executed at least once before the condition is tested.

Syntax

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

Example

This example demonstrates a do-while loop that prints numbers from 0 to 4.

let i: number = 0;

do {
  console.log(i);
  i++;
} while (i < 5);

Output

0
1
2
3
4

Nested While Loop

A nested while loop is a while loop inside another while loop. It allows for more complex iterations.

Example

This example prints a multiplication table for numbers 1 through 3 using nested while loops.

let i: number = 1;

while (i <= 3) {
  let j: number = 1;
  while (j <= 3) {
    console.log(`${i} * ${j} = ${i * j}`);
    j++;
  }
  i++;
}

Output

1 * 1 = 1
1 * 2 = 2
1 * 3 = 3
2 * 1 = 2
2 * 2 = 4
2 * 3 = 6
3 * 1 = 3
3 * 2 = 6
3 * 3 = 9

Complete Example with Output

In this section, we will combine all the examples into a single TypeScript file, compile it to JavaScript, and run it to see the output.

TypeScript Code

You can test the following code in the TypeScript Playground:

// Basic While Loop
let i: number = 0;

while (i < 5) {
  console.log(i); // Output: 0, 1, 2, 3, 4
  i++;
}

// Do-While Loop
i = 0;

do {
  console.log(i); // Output: 0, 1, 2, 3, 4
  i++;
} while (i < 5);

// Nested While Loop
i = 1;

while (i <= 3) {
  let j: number = 1;
  while (j <= 3) {
    console.log(`${i} * ${j} = ${i * j}`); // Output: 1 * 1 = 1, 1 * 2 = 2, ... , 3 * 3 = 9
    j++;
  }
  i++;
}

Conclusion

In this chapter, we covered the while loop in TypeScript, including the basic while loop, do-while loop, and nested while loop. We provided a complete example with its output to illustrate how these loops work in TypeScript. Understanding the while loop is essential for managing loops that require condition-based repetition in TypeScript programs.