Typescript: Type Annotation Example

typeAnnotation.ts

/**
 *  Example: Type Annotation
 *
 *  Type annotations remove the need for the compiler to infer the type.
 *
 *  Available Types:
 *    Boolean:    simple true/false value
 *    Number:     floating point values
 *    String:     textual data
 *    Array:      ordered collection of data
 *    Tuple:      array with fixed number of elements
 *    Enum:       named numeric sets
 *    Any:        unsure of value type
 *    Void:       no value, the opposite of Any
 *
 *
 *  Docs: https://www.typescriptlang.org/docs/handbook/basic-types.html
 */

let thisIsAString: string = "This is my string.";

thisIsAString = 42; // Error: cannot assign 'string' to a 'number'

function createNumber(): number {
  return 55;
}

thisIsAString = createNumber(); // Error cannot assign 'string' to a 'number'