TheCubicleBuddha

function getUserById(id: any){
  // hits a database and returns the value
}

const guid = "b5f770f2-197c-4bf5-a31f-cfec4f545d06";
const user = getUserById(guid);
// ^^^ Runtime Error: PL/SQL: ORA-00932: inconsistent datatypes: expected NUMBER got - TEXT

TheCubicleBuddha

function getUserById(id: any){
  // hits a database and returns the value
}

const guid = "b5f770f2-197c-4bf5-a31f-cfec4f545d06";
const user = getUserById(guid);
// ^^^ Runtime Error: PL/SQL: ORA-00932: inconsistent datatypes: expected NUMBER got - TEXT

TheCubicleBuddha

function getUserById(id: number){
  // hits a database and returns the value
}

const guid = "b5f770f2-197c-4bf5-a31f-cfec4f545d06";
const user = getUserById(guid);
// ^ Compiler error: Argument of type string is not assignable to parameter of type 'number'.

TheCubicleBuddha

function martyrAlgorithm(newUserToSave){
    if(!newUserToSave.lastName){
        throw new Error("I did my best, but I can't save this new user since you didn't get me a lastName")
    }
    globals.databaseHandle.save(newUserToSave);
}

TheCubicleBuddha

import { IUserDbInstance, UserDB } from 'UserDatabase';

interface INewUser {
    firstName: string,
    middleName?: string,
    lastName: string
}

function honestDbMethod(newUserToSave: INewUser, dbInstance: IUserDbInstance){
    // if(newUserToSave.lastName){ // This if statement is unnecessary because you asked for what you need

TheCubicleBuddha

type ITrafficLight =  "red"
                    | "redBlinking" // <-- new case
                    | "green" 
                    | "yellow" 
                    | "yellowBlinking"; // <-- new case

// Can you spot the bug?
//      You can skip ahead to the answer here: https://gist.github.com/TheCubicleBuddha/7a8854f244697b9894e41d44e1fc6967

function respondToTrafficSignal(signal: ITrafficLight): "stop" | "go" | "pause" {

TheCubicleBuddha

type ITrafficLight = "red" | "green" | "yellow";

// Can you see where the function below might go wrong in the future?
//      You can skip ahead to the answer here: https://gist.github.com/TheCubicleBuddha/7a8854f244697b9894e41d44e1fc6967

function respondToTrafficSignal(signal: ITrafficLight): "stop" | "go" | "pause" {
    if(signal === "red"){
        return "stop";
    } else if(signal === "yellow"){
        return "pause";

TheCubicleBuddha

type ITrafficLight = "red" | "redBlinking" | "green" | "yellow" | "yellowBlinking";

function respondToTrafficSignal(signal: ITrafficLight): "stop" | "go" | "pause" {
    if(signal === "red"){
        return "stop";
    } else if(signal === "yellow"){
        return "pause";
    } else if(signal === "green") {
        return "go";
    } else {