How to use 'this' for a generic method function

I’m not sure what the terminology is for this, so apologies if the title is completely off.
I am trying to use the ‘this’ of a method but it’s returning ‘undefined’ when I’m running the code.

I want it to loop through each ‘api’ and call it, then I can go in and do something with the result. Each API can have different parameter data

enum APIPermissions{ HIGH, LOW };
class Api{
  baseurl: string;
  constructor(admin: boolean){
    if(admin){
      this.baseurl = 'localhost';
    }else{
      this.baseurl = 'admin.localhost'
    }
  }

  api1(param1: string){
    return this.baseurl+'/api1 data';
  }

  api2(param1: string, param2: string){
    return this.baseurl+'/api2 data';
  }

  api3(json: any){
    return this.baseurl+'/api3 data';
  }
}
const api = new Api(true);
const data = [
{
    func: api.api1,
    params: ['test1'],
    permissions: [APIPermissions.LOW]
},
{
    func: api.api2,
    params: ['test1', 'test2'],
    permissions: [APIPermissions.HIGH]
}
]
  
for(const d of data){
    const result = d.func('a','b'); // d.params doesn't work
    console.log(result);
    // Check result and do something
}

It’s outputting:
"undefined/api1 data"
"undefined/api2 data"

but I would be expecting "admin.localhost/api1 data". I checked the Typescript docs but the example they give is a bit confusing.
I also don’t know how to get the d.func() part correct as it’s expecting 2 parameters and any help on this too would be appreciated.

>Solution :

Javascript is a bit more dynamic than other languages. When you get a function reference from an object, it’s just the function without a context.

To fix this you need to explicitly bind the functions to an object instance, this will fix the issue you have:

const data = [
  {
    func: api.api1.bind(api),  // bind function to the api object
    params: ['test1'],
    permissions: [APIPermissions.LOW],
  },
  {
    func: api.api2.bind(api),    // bind function to the api object
    params: ['test1', 'test2'],
    permissions: [APIPermissions.HIGH],
  },
];

You can read a bit more about this in here this is not bound.