NodeJs/Javascript access parent method in nested class

Question

class Foo extends EventEmitter {
    constructor(name) {
        this.name = name;
    }
    funcA(sourceRepositoryPath, branch) {

        this.emit('log', 'Hello from Foo');

        var bar = new Bar();
        bar.on('log', function(log) {
            this.emits('log', 'Hello from Foo from Bar');
        });
    }
}

How can i use the emit function from Foo inside the bar.on... function like the

this.emit('log', 'Hello from Foo');

function in ES6?

var foo = new Foo();
foo.funcA();

foo.on('log', function(log) {
    // expects : Hello from Foo && Hello from Foo from Bar 
    // gets : Hello From Foo   
});

Answer 1

The arrow function syntax solves this exact problem:

class Foo extends EventEmitter {
    constructor(name) {
        this.name = name;
    }

    funcA(sourceRepositoryPath, branch) {
        this.emit('log', 'Hello from Foo');

        var bar = new Bar();
        bar.on('log', (log) => {
            this.emits('log', 'Hello from Foo from Bar');
        });
    }
}

Other than a shorter, more concise syntax, arrow functions define a "lexical this", meaning the this keyword inside an arrow function resolves to the instance where the function is defined.