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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

Optional static type annotations

TypeScript allows us to use type annotations to overcome the scenarios in which the type inference system is not powerful enough to automatically detect the type of a variable.

Let's consider the add function one more time:

function add(a, b) {  return a + b;}

The type of the function add is inferred as the following type:

(a: any, b: any) => any;

The preceding type is a problem because the usage of the any type effectively prevents the TypeScript compiler from detecting certain errors. For example, we might expect the add function to add two numbers:

let result1 = add(2, 3); // 5

However, if we pass a string as input, we will encounter an unexpected result:

let result2 = add("2", 3); // "23"

The preceding ...

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Publisher Resources

ISBN: 9781788391474Supplemental Content