Pass an extra argument to a callback function

I have a function callWithMagic which takes a callback function as a parameter and calls it with one argument.

const callWithMagic = callback => {
  const magic = getMagic();
  callback(magic);
};

I also have a function processMagic which takes two arguments: magic and theAnswer.

const processMagic = (magic, theAnswer) => {
  someOtherMagic();
};

I want to pass the function processMagic as an argument to callWithMagic, but I also want to pass 42 as the second parameter (theAnswer) to processMagic. How can I do that?

callWithMagic(<what should I put here?>);

Solution 1:

Just create a function(magic) {} as a wrapper callback:

callWithMagic(function(magic) {
  return processMagic(magic, 42);
});

Or using ECMAScript 6: arrow functions:

callWithMagic(magic => processMagic(magic, 42));

Solution 2:

You could use an anonymus function

something like

session.sub('Hello', function(){marketEvents(your args);});

Solution 3:

You can create a function which calls the marketEvent function. No need to complicate things

session.sub('Hello', function(args, kwargs) {
    marketEvent(args, kwargs, 'my custom data');
});

otherwise you can do this:

var mrktEvent = function(customArgs) {
    return function(args, kwargs) { 
        marketEvent(args, kwargs, customArgs) 
    };
}

session.sub('Hello', mrktEvent("customEvent"));