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everybody knows that arrow functions inside methods ...

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  everybody knows that arrow functions inside methods ... luserdroog <luser.droog@gmail.com> - 2022-03-24 21:57 -0700
    Re: everybody knows that arrow functions inside methods ... Arno Welzel <usenet@arnowelzel.de> - 2022-03-25 09:19 +0100
    Re: everybody knows that arrow functions inside methods ... Elhwen Dico <elhwen.dicote@gmail.com> - 2022-03-25 15:47 +0100
    Re: everybody knows that arrow functions inside methods ... "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2022-03-25 09:32 -0700
    Re: everybody knows that arrow functions inside methods ... JJ <jj4public@gmail.com> - 2022-03-26 11:29 +0700

#40821 — everybody knows that arrow functions inside methods ...

everybody knows that arrow functions inside methods forget their 'this'.
Does everybody else know how to work around that? Does `bind()` do 
something helpful?

-- 
lazy amateur

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#40822

luserdroog:

> everybody knows that arrow functions inside methods forget their 'this'.
> Does everybody else know how to work around that? Does `bind()` do 
> something helpful?

<https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions>


-- 
Arno Welzel
https://arnowelzel.de

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#40824

Le 25/03/2022 à 05:57, luserdroog a écrit :
> everybody knows that arrow functions inside methods forget their 'this'.
> Does everybody else know how to work around that? Does `bind()` do
> something helpful?
> 

Don't know what you mean...

class Test {

     constructor(name) {
         this.name = name;
     }

     getName(delay) {
         setTimeout(
             () => {
                 console.log(this.name);
             }, delay);
     }
}

const t1 = new Test("test 1");
const t2 = new Test("test 2");

t1.getName(500);
t2.getName(100);
->
test 2
test 1

   anonymous arrow function inherits this from the function where it is 
defined (the getName method) whose this is the test object.
   of course

const f = t1.getName;
f(100);
->
D:\xxxxxxxxxxxxxxxxxxxxxxx\test.js:10
                 console.log(this.name);
TypeError: Cannot read properties of undefined (reading 'name')

the call to method getName via f(100) make this to be undefined so is 
this for arrow function

and

const f = t1.getName.bind(t1);
f(100);
->
test 1

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#40827

On Thursday, March 24, 2022 at 11:57:28 PM UTC-5, luser...@gmail.com wrote:
> everybody knows that arrow functions inside methods forget their 'this'. 
> Does everybody else know how to work around that? Does `bind()` do 
> something helpful? 

You use a function instead of a lambda. This is by design.

The alternative is to pass 'this' as an explicit argument:

(self, foo) => {...}

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#40829

On Thu, 24 Mar 2022 21:57:24 -0700 (PDT), luserdroog wrote:
> everybody knows that arrow functions inside methods forget their 'this'.
> Does everybody else know how to work around that? Does `bind()` do 
> something helpful?

Arrow function is not a replacement or a "better" version of the normal
function. Both have different purposes.

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