TypeScript: Modern JavaScript Development

Type checking

The compiler will check the types of your code. It has several primitive types and you can define new types yourself. Based on these types, the compiler will warn when a value of a type is used in an invalid manner. That could be using a string for multiplication or using a property of an object that does not exist. The following code would show these errors:

let x = "foo"; 
x * 2; 
x.bar(); 

TypeScript has a special type, called any, that allows everything; you can assign every value to it and you will never get type errors. The type any can be used if you do not have an exact type (yet), for instance, because it is a complex type or if it is from a library that was not written in TypeScript. This means that the following code gives ...