Examples of Typescript

test.ts

// ?. Mixed with the type system

let thing: number | undefined | string | { descripcion: string } = 1;
console.log(thing?.descripcion); // => test.ts(2,20): error TS2339: Property 'descripcion' does not exist on type 'number'.

thing = "test";
console.log(thing?.descripcion); // => test.ts(5,20): error TS2339: Property 'descripcion' does not exist on type 'string'.

thing = { descripcion: "test" };
console.log(thing?.descripcion); //=> test.ts(11,20): error TS2339: Property 'descripcion' does not exist on type 'string | number | { descripcion: string; }'.

thing = undefined;
console.log(thing?.descripcion); // => undefined

// const in ts and js
const constTest: { prop1: string } = { prop1: "test" };
console.log(constTest.prop1); //=> test

constTest.prop1 = "replaced";
console.log(constTest.prop1); //=> replaced

constTest = { ...constTest }; //=> test.ts(8,1): error TS2588: Cannot assign to 'constTest' because it is a constant.
console.log(constTest.prop1);

// Fetch query
const [
    loadCarsByVIN, // -> Call that you need to trigger to pull data `loadCarsByVIN({variables: {vin: "exampleVin"}})`;
  // true/false      error message on fail     function mock server response    query result.    pull data ignores cache
  //      |                   |                              |                        |                       |
  { loading,                 error,                     updateQuery,                data,                 refetch,                       called },
] = useLazyQuery<CarByVINData, CarByVINVars>(CarByVIN);