Why my function secondMethod is not a function TypeError: (...).secondMethod is not a function

Question

I am try to make a chainable instance for a personal project, and I try this simple example with some modifications, but I got a error:

TypeError: chainableInstance.firstMethod(...).secondMethod is not a function
    at Object.<anonymous> (/Users/rodger/Developer/Projects/Personal/unknown/src/teste.js:48:33)
    at Module._compile (internal/modules/cjs/loader.js:1200:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1220:10)
    at Module.load (internal/modules/cjs/loader.js:1049:32)
    at Function.Module._load (internal/modules/cjs/loader.js:937:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:71:12)
    at internal/main/run_main_module.js:17:47

And my code is this:

  otherMethod(a) {
    return (this.a = a.replace('!e', 'e'));
  }
}
class Another extends Other {
  constructor() {
    super();
  }

  anotherMethod(a) {
    console.log('This is anohter method');
    return (this.a = a.replace('!d', 'd !e'));
  }

  otherMethod() {
    return super.otherMethod(this.a);
  }
}

class ChainAble extends Another {
  constructor() {
    super();
  }

  firstMethod() {
    return (this.a = 'a !b');
  }

  secondMethod() {
    return this.a.replace('!b', 'b !c');
  }

  thirdMethod() {
    return this.a.replace('!c', 'c !d');
  }
  anotherMethod() {
    return super.anotherMethod(this.a);
  }
}

const chainableInstance = new ChainAble();
chainableInstance.firstMethod().secondMethod().thirdMethod().anotherMethod();

console.log(chainableInstance);

I just not undestand why my secondMethod is It is considered "not a function", have someone to see what I am wrong in this stuff?

Calling some class `Chainable` doesn't make it chainable. You actually need to return an instance from the first method for that! None of your methods even returns an object. — Bergi, May 30 '20 at 16:25
Does this answer your question? [Method Chaining in a Javascript Class](https://stackoverflow.com/questions/48219415/method-chaining-in-a-javascript-class) — Ivar, May 30 '20 at 16:26

vadimk7 · Answer 1 · 2020-05-30T18:20:00.183

1

It's because firstMethod returns the string 'a !b' (the result of assignment). You need to return directly this from any methods that need to be chainable

edited May 30 '20 at 18:20

answered May 30 '20 at 16:27

vadimk7

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score 1 · Accepted Answer · answered May 30 '20 at 16:29

this is what you need

Example

class Another {
  constructor() {
  }

  anotherMethod(a) {
    console.log('This is anohter method');
    this.a = a.replace('!d', 'd !e');
    return this;
  }

  otherMethod() {
    return super.otherMethod(this.a);
  }
}

class ChainAble extends Another {
  constructor() {
    super();
  }

  firstMethod() {
    this.a = 'a !b';
    return this;
  }

  secondMethod() {
    this.a = this.a.replace('!b', 'b !c');
    return this;
  }

  thirdMethod() {
    this.a = this.a.replace('!c', 'c !d');
    return this;
  }
  anotherMethod() {
    return super.anotherMethod(this.a);
  }
}

const chainableInstance = new ChainAble();
chainableInstance.firstMethod().secondMethod().thirdMethod().anotherMethod();

console.log(chainableInstance);

Why my function secondMethod is not a function TypeError: (...).secondMethod is not a function

2 Answers2