Alibaba Beijing Interview Round 1

1. What are JS primitive data types?
   1. What's the use of Symbol?
   2. Have you used BigInt?
2. Tell me about prototype chain.
3. How do you implement a virtualized list? solution
4. Map vs plain object? MDN solution
5. flexbox
6. How to narrow a variable's type in typescript?

Programming

Curry

Implement the following function

// add(5, 2)  7
// add(5)(2)  7
function curry(func) {
  return function curried(...args) {
    if (args.length >= func.length) {
      return Reflect.apply(func, undefined, args);
    } else if (args.length < func.length) {
      return (...a) => curried(...args, ...a);
    }
  };
}

function add(a, b) {
  return a + b;
}
const curriedAdd = curry(add);
console.log(curriedAdd(2)(5)); // 7
console.log(curriedAdd(2, 5)); // 7

Sort

Sort an array, even number on the left (in descending order), odd number on the right (in ascending order) and 0 in the middle.

// [1,4,5,2,7,0]   =>   [4,2,0,1,5,7]