ES6: Accessing to class'es 'this' from inner local function

Question

In below example, I need to access this.methodWhichRequredAnywhere() inside functionWhichRequiredInConstructorOnly().

class Example(){

    construtor(){

        function functionWhichRequiredInConstructorOnly(){
             // warning: invalid code
            return this.methodWhichRequredAnywhere + ' complete';
        }

        this.message = functionWhichRequiredInConstructorOnly();
    }

    methodWhichRequredAnywhere(){
        return 'test';
    }
}

Too much explanation about closures in answers to another questions, but I still did not found simple solution to solve above problem.

Note

I understand that above code architecture is contradicting to OOP. Why I used it?

I suppose, functionWhichRequiredInConstructorOnly() will be utilized after constructor will be executed. Will methodWhichRequredAnywhere be?
I need to group come declarations in my real class. So functionWhichRequiredInConstructorOnly() goes directly below some declarations where it used.

Turn `functionWhichRequiredInConstructorOnly` into an arrow function — CertainPerformance, May 03 '18 at 01:09
@CertainPerformance, `functionWhichRequiredInConstructorOnly = () => { /* ... */}` - this way? `functionWhichRequiredInConstructorOnly () => { /* ... */}` will be invalid... — Takesi Tokugawa YD, May 03 '18 at 01:10
Yep, though you would put `const` in front of it so as not to implicitly create a global variable, I'm sure there are many posts about this sort of thing — CertainPerformance, May 03 '18 at 01:12
@CertainPerformance - `many posts` - countless, on a daily basis :p — Jaromanda X, May 03 '18 at 01:28

score 2 · Accepted Answer · answered May 03 '18 at 01:12

You need to call the function and explicitly set its this value to the value you want. You can do that with .call:

this.message = functionWhichRequiredInConstructorOnly.call(this);

Or define the function as an arrow function as suggested in the comments. Arrow functions don't have their own this binding but resolve it lexically just like any other variable.

How to access the correct `this` inside a callback? (though you are not having a callback here)
How does the "this" keyword work?

ES6: Accessing to class'es 'this' from inner local function

Note

1 Answers1