metaize-action.js

function test(params) {
  return {
    type: 'TEST',
    payload: params
  }
}

const metaizeThis = (fn) => {
  fn._meta = {};
  fn.addMeta = function(meta) {
    if(!this._originalFunction) {
      this._originalFunction = this;
      this._originalFunction._meta = {};
    }
    this._originalFunction._meta = {...this._originalFunction._meta, ...meta}
    
    
    const wrapped = (...params) => {
      const result = this(...params);
      result.meta = {...this._meta,...meta};
      return result
    }
    
    wrapped.addMeta = this.addMeta;
    wrapped._originalFunction = this._originalFunction;
    wrapped._meta = this._originalFunction._meta;
  
    return wrapped;
  }
  
  return fn;
}

const wm = metaizeThis(test).addMeta({test: 1}).addMeta({ook: 2}).addMeta({lue: 42});
const wm2 = metaizeThis(test).addMeta({um: 1}).addMeta({oooohThisIsBad: true});
console.log(wm(1));
console.log(wm2(1));

/*
Object {
  "meta": Object {
    "lue": 42,
    "ook": 2,
    "test": 1
  },
  "payload": 1,
  "type": "TEST"
}
Object {
  "meta": Object {
    "oooohThisIsBad": true,
    "um": 1
  },
  "payload": 1,
  "type": "TEST"
}
*/

What is going on here? I'm going to try and decipher this over the weekend, but I would love some commentary from you.