Conditional Statements and Loop Control in TypeScript | CodeSignal Learn

Conditional Statements and Loop Control in TypeScript | CodeSignal Learn

Introduction

Welcome! In this lesson, we're exploring special instructions in the TypeScript language: Conditional Statements, along with the break and continue statements. As we've learned, loops allow us to execute a block of code numerous times. By combining these loops with conditional statements and incorporating the useful break and continue instructions, we achieve more robust and efficient code. A key feature of TypeScript is its type-checking, which enhances the reliability of your conditions. Let's dive in!

The 'if' Statement

In TypeScript, the if statement triggers actions in our code based on a specific condition. Consider this straightforward example, where the if statement determines which message to print based on the value of temperature : TypeScript let temperature: number = 15; if (temperature > 20) {console.log("Wear light clothes."); // This message will print if the temperature is over 20.} else {console.log("Bring a jacket."); // This message will print otherwise.} // Output: Bring a jacket.

The "else if" Statement

We can evaluate multiple conditions using else if . This phrase means, "If the previous condition isn't true, then check this one": TypeScript let temperature: number = 15; if (temperature > 30) {console.log("It's hot outside!"); // This will print if the temperature is over 30.} else if (temperature > 20) {console.log("The weather is nice."); // This will print if the temperature is between 21 and 30.} else {console.log("It might be cold outside."); // This will print if the temperature is 20 or below.} // Output: It might be cold outside.

The 'break' Statement

We use the break statement whenever we want to exit a loop prematurely once a condition is met: TypeScript const numbers: number[] = [1, 3, 7, 9, 12, 15]; for (let i: number = 0; i < numbers.length; i++) {if (numbers[i] % 2 === 0) {console.log("The first even number is: " + numbers[i]); // This prints the first even number. break; // This stops the loop after printing the first even number.} console.log("Number: " + numbers[i]);} // Output: // Number: 1 // Number: 3 // Number: 7 // Number: 9 // The first even number is: 12

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The 'continue' Statement

The continue statement bypasses the rest of the loop code for the current iteration only: for (let i: number = 0; i < 6; i++) {if (i === 3) {continue; // This skips the print command for '3'.} console.log(i); // This prints the numbers from 0 to 5, except 3.} // Output: // 0 // 1 // 2 // 4 // 5

Use-case with a For Loop

By utilizing the tools we've covered so far, we can craft more flexible loops. Here's a snippet where we terminate the loop once we find "Charlie": const names: string[] = ["Alice", "Bob", "Charlie", "David", "Charlie"]; for (const name of names) {if (name === "Charlie") {console.log("Found Charlie!"); // This prints when 'Charlie' is found. break; // This stops the loop after finding 'Charlie'.}} // Output: // Found Charlie!

TypeScript

for (let i: number = 0; i < 6; i++) {
    if (i === 3) {
        continue; // This skips the print command for '3'.
    }
    console.log(i); // This prints the numbers from 0 to 5, except 3.
}
// Output:
// 0
// 1
// 2
// 4
// 5

TypeScript

const names: string[] = ["Alice", "Bob", "Charlie", "David", "Charlie"];

for (const name of names) {
    if (name === "Charlie") {
        console.log("Found Charlie!"); // This prints when 'Charlie' is found.
        break; // This stops the loop after finding 'Charlie'.
    }
}
// Output:
// Found Charlie!