How to add type to make below code not prompt type errors in typescript

Question

const obj = {
  extend: (p: {
    property: string;
    methods: { name: string; call: string; params: number }[];
  }) => {
    obj[p.property] = {};
    p.methods.forEach((m) => {
      obj[p.property][m.name] = (params: any[]) =>
        m.call + "____" + params.length;
    });
  },
};

obj.extend({
  property: "Scope1",
  methods: [
    {
      name: "functionName",
      call: "function_name",
      params: 1,
    },
  ],
});
// How to add type to make below code not prompt type errors in typescript. In typescript, this code below will prompt type errors.
console.log(obj["Scope1"].functionName(["firstParam"]));

How to add type to make that code not prompt type errors in typescript. obj extend methods, all the methods were putted in one property.

score 0 · Answer 1 · answered May 17 '22 at 06:45

You have a very generic Requirement regarding how the extend() work.

To avoid the type errors and make it generic we can define an ObjectTemplate to satisfy the Typescript compiler so that we can assign a value to the object on the fly.

type Args = {
    property: string;
    methods: { name: string; call: string; params: number }[];
}

type ObjTemplate = {
  extend: (args: Args) => void;
  [k: string]: any
}

const obj: ObjTemplate = {
  extend: (p: Args) => {
    obj[p.property] = {};
    p.methods.forEach((m) => {
      obj[p.property][m.name] = (params: any[]) =>
        m.call + "____" + params.length;
    });
  }
};

obj.extend({
  property: "Scope1",
  methods: [
    {
      name: "functionName",
      call: "function_name",
      params: 1,
    },
  ],
});

console.log(obj["Scope1"].functionName(["firstParam"]));

Code Playground

score 0 · Answer 2 · answered May 17 '22 at 09:44

According to typescript-interface-problem I find one answer.


export const obj = {
  extend: <T extends string, O extends string>(a: {
    property: T;
    methods: { name: O; call: string; params: number }[];
  }): {
    [Prop in typeof a as Prop["property"]]: {
      [Prop in typeof a.methods[number] as Prop["name"]]: (
        ...args: any
      ) => Promise<any>;
    };
  } => {
    const obj = {} as any;
    a.methods.forEach((method) => {
      obj[method.name] = (...args: any) => {
        return Promise.resolve("success");
      };
    });

    const newObject = {
      [a.property]: obj,
    };

    return newObject;
  },
};

const extendedObj = obj.extend({
  property: "Scope1",
  methods: [
    {
      name: "functionName",
      call: "function_name",
      params: 1,
    },
  ],
});

After that, we can get this.

Welcome to SO! Could you please explain what exactly you did to solve their problem? Or summarize what you learned from the link you referenced? [Here](https://stackoverflow.com/help/how-to-answer) is a good reference for what to include in an answer. Thanks for participating in the community! — anbcodes, May 17 '22 at 15:57

How to add type to make below code not prompt type errors in typescript

2 Answers2