a quick bind

mybind.js

function myBind(fn, context, ...args) {
  return function(...moreArgs) {
    return fn.call(context, ...(args.concat(moreArgs)));
  }
}

// test
function add(a,b,c) {
  return a + b + c;
}

console.log(myBind(add, null, 1,2)(3)) // 6