is-this-partial-application.js

// So what I'm doing here seems cool, but I'm not sure exactly what it's called.
// (also, I'm not doing anything smart here with execution context)

function partial( orig_func ) {
  var ap = Array.prototype,
    partial_args = ap.slice.call( arguments, 1 ),
    invoked_args;
  
  function fn() {
    var result;
    // allow for more than just one argument to be added to invoked_args per call:
    invoked_args = ap.concat.apply( invoked_args || partial_args.slice(), ap.slice.call( arguments) );
    
    if ( invoked_args.length < orig_func.length ) {
      return fn;
    } else {
      result = orig_func.apply( this, invoked_args );
      invoked_args = 0;
      return result;
    }
  };
  
  return fn;
};

function a( x, y, z ) {
  console.log( x + ' and ' + y + ' or ' + z );
};

a( 'x', 'y', 'z' ); // "x and y or z"

var b = partial( a );
b('u')('v')('w'); // "u and v or w"

var c = partial( a, 'r' );
c('s')('t'); // "r and s or t"

var d = partial( a, 'o', 'p' );
d('q'); // "o and p or q"
d('n'); // "o and p or n"

var e = partial( a, 'w');
e('t','f'); // "w and t or f"