Javascript ES6 spread operator on undefined [duplicate]

Answer 1

This behavior is useful for doing something like optional spreading:

function foo(options) {
  const bar = {
    baz: 1, 
    ...(options && options.bar) // options and bar can be undefined
  } 
}

And it gets even better with optional chaining, which is in Stage 4 now (and already available in TypeScript 3.7+):

function foo(options) {
  const bar = {
    baz: 1, 
    ...options?.bar //options and bar can be undefined
  } 
}

a thought: its too bad it doesn't also work for spreading into an array