Hack Reactor Interview History

HackReactorJsTest.js

each([1, 2, 3], function (val) {
  console.log(val);
});

// 1
// 2
// 3

var each = function (array, callback) {
    // Including array.length as variable declaration to "cache" it
    for(var i=0,arrayLength=array.length; i<arrayLength; i++){
        callback(array[i]);
    }
};

map([1, 2, 3, 4], function (val) {
  return val * 2;
}); //=> [2, 4, 6, 8]

var map = function (array, callback) {
  var newArray = [];
  each(array, functions,.returnedValue) {
    // modify newArray here
    newArray.push(callback(returnedValue));
  });
  return newArray;
};

filter([1, 2, 3, 4], function (val) {
  return val > 2;
}); //=> [3, 4]

var filter = function (array, truthTest) {
  var truthyArray = [];
  each(array, function(returnedValue){
      // Ternary wasn't working out, go with the conservative if/else
      if(truthTest(returnedValue){
          truthyArray.push(returnedValue);
      }else{
          // End function execution
          return;
      }
  });
  return truthyArray;
};