Introduction
In this chapter, we will explore the do-while loop in TypeScript. The do-while loop is a control flow statement that allows you to execute a block of code at least once, and then repeatedly execute the block as long as a specified condition is true. Understanding how to use the do-while loop is essential for managing loops that need to execute at least once before checking a condition in TypeScript programs.
Table of Contents
- Definition
- Do-While Loop Syntax
- Basic Do-While Loop
- Using Do-While Loop with Arrays
- Nested Do-While Loop
- Complete Example with Output
- Conclusion
Definition
The do-while loop repeats a block of code at least once, and then continues to repeat as long as a specified condition is true. This loop is useful when you need the code to run at least once regardless of the condition.
Do-While Loop Syntax
Syntax
do { // code to be executed } while (condition); Example
This example demonstrates a basic 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 Basic Do-While Loop
The basic do-while loop ensures that the code block is executed at least once before the condition is tested.
Example
This example prints the first five even numbers using a do-while loop.
let num: number = 0; do { console.log(num); num += 2; } while (num < 10); Output
0 2 4 6 8 Using Do-While Loop with Arrays
The do-while loop can be used to iterate over the elements of an array.
Example
This example iterates over an array of colors and prints each one using a do-while loop.
let colors: string[] = ["red", "green", "blue"]; let index: number = 0; do { console.log(colors[index]); index++; } while (index < colors.length); Output
red green blue Nested Do-While Loop
A nested do-while loop is a do-while loop inside another do-while loop. It allows for more complex iterations.
Example
This example prints a multiplication table for numbers 1 through 3 using nested do-while loops.
let i: number = 1; do { let j: number = 1; do { console.log(`${i} * ${j} = ${i * j}`); j++; } while (j <= 3); i++; } while (i <= 3); Output
1 * 1 = 1 1 * 2 = 2 1 * 3 = 3 2 * 1 = 2 2 * 2 = 4 2 * 3 = 6 3 * 1 = 3 3 * 2 = 6 3 * 3 = 9 Complete Example with Output
In this section, we will combine all the examples into a single TypeScript file, compile it to JavaScript, and run it to see the output.
TypeScript Code
You can test the following code in the TypeScript Playground:
// Basic Do-While Loop let i: number = 0; do { console.log(i); // Output: 0, 1, 2, 3, 4 i++; } while (i < 5); // Using Do-While Loop with Arrays let colors: string[] = ["red", "green", "blue"]; let index: number = 0; do { console.log(colors[index]); // Output: red, green, blue index++; } while (index < colors.length); // Nested Do-While Loop i = 1; do { let j: number = 1; do { console.log(`${i} * ${j} = ${i * j}`); // Output: 1 * 1 = 1, 1 * 2 = 2, ... , 3 * 3 = 9 j++; } while (j <= 3); i++; } while (i <= 3); Conclusion
In this chapter, we covered the do-while loop in TypeScript, including the basic do-while loop, using do-while loop with arrays, and nested do-while loops. We provided a complete example with its output to illustrate how these loops work in TypeScript. Understanding the do-while loop is essential for managing loops that need to execute at least once before checking a condition in TypeScript programs.