Writing less verbose code with the type inference of TypeScript

Static typing has a number of benefits; however, it makes us write a more verbose code by adding all the type annotations.

In some cases, the compiler of TypeScript is able to guess the types of expressions inside our code; let's consider this example:

let answer = 42; 
answer = '42'; // Type "string" is not assignable to type "number" 

In the preceding snippet, we defined an answer variable and assigned the value 42 to it. Since TypeScript is statically typed and the type of a variable cannot change once declared, the compiler is smart enough to guess that the type of answer is number.

If we don't assign a value to a variable within its definition, the compiler will set its type to any:

let answer; 
answer = 42; 
answer = '42'

The preceding snippet will compile without...