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Learning TypeScript 2.x - Second Edition
book

Learning TypeScript 2.x - Second Edition

by Remo H. Jansen
April 2018
Beginner content levelBeginner
536 pages
13h 21m
English
Packt Publishing
Content preview from Learning TypeScript 2.x - Second Edition

Functions with optional parameters

Unlike JavaScript, the TypeScript compiler will throw an error if we attempt to invoke a function without providing the exact number and types of parameters that its signature declares. Let's look at a code sample to demonstrate this:

function add(foo: number, bar: number, foobar: number): number { 
    return foo + bar + foobar; 
} 

The preceding function is called add and will take three numbers as parameters, named foo, bar, and foobar. If we attempt to invoke this function without providing exactly three numbers, we will get a compilation error indicating that the supplied parameters do not match the function's signature:

add(); // Error, expected 3 arguments, but got 0. add(2, 2); // Error, expected 3 arguments, ...
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Publisher Resources

ISBN: 9781788391474Supplemental Content