How does prototype extend on typescript?

Question

i extended function prototype but typescript doesn't recognize it.

Function.prototype.proc = function() {
  var args, target, v;
  var __slice = [].slice;
  args = 1 <= arguments.length ? __slice.call(arguments, 0) : [];
  target = this;
  while (v = args.shift()) {
    target = target(v);
  }
  return target;
};
// generated by coffee-script

var foo: (number) => (string) => number
  = (a) => (b) => a * b.length;
console.log(foo.proc("first", "second"))

result: tsc -e

The property 'proc' does not exist on value of type 'Function'

how do i extend this object?

Answer 1

There is a Function interface in the standard typescript lib which declares the members of Function objects. You will need to declare proc as a member of that interface with your own add on like the following:

interface Function {
    proc(...args: any[]): any;
}

This interface will need to be referenced from anywhere you intend to use 'proc'.

Answer 2

Like this:

declare global {
    interface Function {
        proc() : any;
    }
}

Without 'declare global' it doesn't work.

That's how module augmentation works in recent TypeScript versions. Check out the documentation and scroll down to the Module augmentation section.