syncify.js

syncify.js

// 1. fn's last argument should be a callback
// 2. the syncified function returns an array, which is the arguments for that callback.
function syncify (fn) {
  let doing = true
  return function (...args) {
    let result = undefined
    fn(...args, (...callbackArgs) => {
      result = callbackArgs
      doing = false
    })
    while (doing) {}
    return result
  }
}