anyPartialApplication

any-partial-application.js

const div = (verbed, numerator, denominator) =>
  `${numerator} ${verbed} ${denominator} is ${numerator/denominator}`
  
div('divided by', 1, 3)
  //=> 1 divided by 3 is 0.3333333333333333
  
const anyPartialApplication = (() => {
  const placeholder = {},
        anyPartialApplication = (fn, ...template) => {
          let remainingArgIndex = 0;
          const mapper = template.map((templateArg) =>
                           templateArg === placeholder
                             ? ((i) => (args) => args[i])(remainingArgIndex++)
                             : (args) => templateArg);
          
          return function (...remainingArgs) {
            const composedArgs = mapper.map(f => f(remainingArgs));
            
            return fn.apply(this, composedArgs);
          }
          
        };
        
  anyPartialApplication._ = placeholder;
  return anyPartialApplication;
})();

const _ = anyPartialApplication._;

const dividedByThree = anyPartialApplication(div, 'divided by', _, 3);

dividedByThree(2)
  //=> 2 divided by 3 is 0.6666666666666666