Mastering TypeScript/

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Function Signatures and the void Keyword

Function Signatures and the void Keyword

Learn how to use type annotations in TypeScript to strongly type function signatures.

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Function signatures in TypeScript

One of the best features of using type annotations in TypeScript is that they can also be used to strongly type function signatures.

To explore this feature a little further, let’s write a JavaScript function to perform a calculation as follows:

// This function calculates the result of (a * b) + c
function calculate(a, b, c) {
  
  // Return the result of (a * b) + c
  return (a * b) + c;
  }
// Log the result of calling the calculate function with arguments 3, 2 and 1
console.log("calculate() = " + calculate(3, 2, 1));
Calculate function with numbers

Here, we have defined a JavaScript function named calculate from lines 2 — 6 that has three parameters, a, b, and c.

Within this function, we are multiplying a and b, and then adding the value of c.

The result is correct, as 2∗3=62 * 3 = 6 ...