passing user-defined variables to the callback function

[davelandry]

I have an ES6 Class function that I'd like to invoke as a callback function, but it loses the scope of this when I call it with timer(callback).

Any way we can pass a custom variable to the callback function? I'm not quite sure how the syntax would even look, as I wouldn't want to override the delay and time variables.

[mbostock]

Did you consider using function.bind or a closure? Say you have an instance of your class (here described as a literal, but the use of ES6 classes or fields inherited properties doesn’t affect the solution):

var fred = {
  hello: function() {
    console.log("Hi, my name is " + this.name + ".");
    return true;
  },
  name: "Fred"
};

Invoking the hello method:

fred.hello(); // prints "Hi, my name is Fred.", returns true

Invoking this method by timer using a closure:

timer(function() {
  return fred.hello();
});

Invoking this method by timer using function.bind:

timer(fred.hello.bind(fred));

Note that you can also use a closure to pass extra arguments to your callback. For example, say you have a function:

function hello(name) {
  console.log("Hi, my name is " + name + ".");
  return true;
}

Invoking this method by timer using a closure:

timer(function() {
  return hello("Fred");
});

[davelandry]

Egg on my face, obviously the bind works great. Thanks so much for the thorough response and great work with these new modules!