Pluck, Unique, and Compose from scratch in JS

pluck-unique-and-compose.js

  function pluck(property, collection) {
    return collection.map(function(e){
      return e[property];
    });
  }

  // return an array with unique elements
  // this isn't efficient for sorted arrays, but whatevs
  function unique(collection) {
    // ternary operator to guard for empty collection
    var length = collection ? collection.length : 0;

    if (!length) { return []; }

    var seen = [];
    collection.forEach(function(e) {
      if ( seen.indexOf(e) < 0 ) { seen.push(e); }
    });
    return seen;
  }
  
    // compose two functions together
  function compose(func1, func2) {
    return function() {
      return func1(func2.apply(null, arguments));
    };
  }

  var distinct = compose(unique, pluck);