Typescript Runtime Typeguards

ts_type_guards.ts

// Asserts data is an array of values that pass a certain check
// Once the assertion passes (not throwing), TS will infer the proper type 
function assertIsTypedArray<T>(arg: any, check: (value: any) => value is T): asserts arg is T[] {
  if (!Array.isArray(arg)) throw new Error(`This is not an array: ${JSON.stringify(arg)}`);
  if (arg.some((el) => !check(el)))
    throw new Error(`Some elements of the array are not the expected type:  ${JSON.stringify(arg)}`);
}

// exemple of check function

// function isITeam(arg: any): arg is ITeam {
//   return (
//     typeof arg.iconUrl === 'string' &&
//     typeof arg.name === 'string' &&
//     typeof arg.id === 'string' &&
//     Array.isArray(arg.channels)
//   )
// }