how can I retrieve a reference to this in a promise.then ()?

Question

javascript / Node.js

how can I retrieve a reference to this/object inside a promise.then ?

var controller = new MyController(params);

controller.action_send();

/////////////////////////////////

class MyController{

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

    action_send()
    {
        var promise = ext_lib.send();


        promise.then(
            function(details) {

                this.action_save(details);
                //(node:27014) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'action_save' of undefined
           });
   }

    action_save(details)
    {  
     save (this.params, details);
    }   
}

a PHPStorm warning says Warns against a common mistake of trying to reference a member of an ECMAScript class via this. qualifier in a nested function that is not a lambda. this in a nested function that is not a lambda is the function's own 'this' and doesn't relate to the outer class.

tks from now

Answer 1

Use an arrow function.

Unlike a regular function, an arrow function does not bind this. Instead, this is bound lexically (i.e. this keeps its meaning from its original context).

Here are more details about it Arrow Functions