map.ts

/** 
 * A generator function which maps a function across an iterable of values.
 */
function map(fn, items) {  // Add typings to the function definition
  // Implement the body of the function
}


interface HasLength {
  length: number;
}


function getLength<T extends HasLength>(thing: T): number {
  return thing.length;
}


// Example Usage
for (let length of map(getLength, ['cat', 'dog', 'mouse', 'canada'])) {
    console.log(length);
}