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Passing a javascript method as an argument

I’ve been around javascript for a long time, but am pretty rusty with javascript Classes. For a particular project I’m working on, things are starting to get unwieldy and I’d like to start cutting up my code into separate files. I don’t want to have to import all my functions explicitly, so I’ve started wrapping them up into a Class (which makes sense for other reasons also). Some of my functions return callbacks (functions). That is:

return functionName;

Which I can use like:

var callBack = functionReturningFunction();
...
callBack();

I cannot find any information about returning and passing methods, rather than functions what is the syntax there? Ideally I’d like to pass in methods as arguments to the constructor so I can say:

const myObject = new MyClass(methodName);

So I don’t have to do:

const myObject = new MyClass();
myObject.methodName();
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2

Answers


  1. Chosen as BEST ANSWER
    0

    The stackoverflow fairy brought me the answer as I was finishing typing out the question. Following the pattern in my question, I have:

    return this.methodName;

    Which I can use like:

    var callBack = myObject.methodReturningMethod();
...
callBack();

    From outside my Class. Importantly I should have:

    methodReturningMethod(){
 ...
 return this.aMethod.bind(this);
}

    inside methodReturningMethod() if aMethod() accesses any object properties because javascript is * special * like that (and will get all confused if I don't).

    Inside class methods I can have stuff like:

    this.callBackMethod = this.methodReturningMethod();
...
this.callBackMethod();

    which will call whichever method this.methodReturningMethod() returns.

    I don't think its possible to specify an object method as a parameter to that object's constructor because object methods don't exist before the object has been constructed. Shout out if you know a way. After the object has been created I can do things like:

    myObject.methodReceivingMethod(myObject.method);

  2. 0

    Just basic common info for your:

    I don’t want to have to import all my functions explicitly

    You don’t need class to provide them in NamesSpaces

    You can create file helper.js:

    export function one() {}
export function two() {}
export function three() {}

    and then basicly include them from:

    import * as Helper from "./helper.js"
Helper.one()
Helper.two()
Helper.three()
    1. If you like Classes and want to create new isntance, then you should know about "static" feature.
    export class Helper {
  static one() {}
  static two() {}
  static three() {}
}

    and then …

    import { Helper } from "./helper.js"
Helper.one()
Helper.two()
Helper.three()
    1. Probably if you can tell more about your case I can figure our more ways to solve it.

    Good Luck with your project! 😉

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