JavaScript partially applied function - How to bind only the 2nd parameter?

Question

Sorry if I\'m missing something obvious, but I can\'t figure out how to bind a specific (nth) argument of a function in javascript. Most of my functional programming I\'ve

Answer 1

you can try this:

Function.prototype.bindThemAll = function bindThemAll(thisArg, ...boundArgs) 
  (boundArgs.fn = this, function(...args) boundArgs.fn.call(thisArg || this, ...boundArgs.map((el) => el || args.shift()), ...args));

function fn() console.log("fn:", arguments.callee, "this:", this, "args:", arguments)

var x = {a: 5};

var bfn = fn.bindThemAll(x, null, 2)
bfn(1,3)
x.bfn = fn.bindThemAll(null, null, 2)
x.bfn(1,3)

bound arguments with null or undefined will be replaced with the function arguments in order, the remaining arguments will be appended to the end. an object will be used if it is bound otherwise the current this will be used...

see console for results!