Pass an extra argument to a callback function

Question

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?>); 

Answer 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)); 

Answer 2

You could use an anonymus function

something like

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