The answer
fn.length is the number of parameters declared in the original function. The curry function uses it to know when enough arguments have been collected to call the original function.
Currying Implementation and Examples
What is fn.length in the curry function?
More FAQs in Currying Implementation and Examples
Use nested functions: function multiply(a) { return function(b) { return function(c) { return a * b * c; }; }; }. Each function takes one argument and returns the next.
Return a function that collects arguments. If args.length >= fn.length, call fn(...args). Otherwise, return (...next) => curried(...args, ...next). Use recursion to keep collecting.
Configurable functions: const log = curry((level, msg) => ...); const error = log('ERROR'); error('something broke'). Each partial call creates a specialized function.
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