Underscore Method Implementations

underscoreIMPS.js

//#######PLUCK#######

var myPluck = function(obj, propName) {
    var arr = [];
    for (var i = 0; i < obj.length; i++) {
        for (var prop in obj[i]) {
            if (prop === propName)
                arr.push(obj[i][prop]);
        }
    }
    return arr;
}

//tests
var stooges = [{name: 'moe',age: 40}, {name: 'larry',age: 50}, {name: 'curly',age: 60}];
console.log(myPluck(stooges, 'name')); //[ 'moe', 'larry', 'curly' ]
console.log(myPluck(stooges, 'age')); // [ 40, 50, 60 ]

//#######FILTER#######

var myFilter = function(obj, callback, context){
  var arr = [];
  obj.forEach(function(el){
    if(callback.call(context, el, obj))
      arr.push(el);
  });
  return arr;
};

//tests
var str = ['Zed', 'zeek', 'Zoro', 'god', 'jumanji'];
var newFilter = myFilter(str, function(str){
   return str[0] === 'Z';
});

console.log(newFilter); //[ 'Zed', 'Zoro' ]


//#######WHERE#######//FOR ONLY ONE PROPERTY, DOES NOT WORK FOR MULTIPLE

var myWhere = function(obj, objProp) {
    //intialize empty array to return
    var arr = [],
        property, value;
    //get property and object we're checking for by
    //breaking object passed into individual components
    for (var prop in objProp) {
        property = prop;
        value = objProp[property];
    }
    //now go through each object and check to see which
    //objects have the properties and values we seek
    obj.forEach(function(ob) {
        for (var prop in ob) {
            if (prop === property && ob[prop] === value) {
                arr.push(ob);
            }
        }
    });
    return arr;
};

//tests
var input = [ { name: 'Tiger', space: 7}, { name: 'Tiger2', space: 1}, { name: 'Tiger3', space: 3}, { name: 'Tiger4', space: 3} ];
var output = myWhere(input, {
    space: 3
});
console.log(output); // [ { name: 'Tiger3', space: 3 }, { name: 'Tiger4', space: 3 } ]
var output = myWhere(input, {
    space: 7
});
console.log(output); // [ { name: 'Tiger', space: 7 } ]


//#############EACH###################

var myEach = function(obj, callback) {
    //first check if object is array
    if (typeof obj.length === 'number') {
        for (var i = 0; i < obj.length; i++) {
            callback(obj[i], i, obj);
        }
    }
    //otherwise we'll assume an Object object was passed
    else {
        for (var prop in obj) {
            callback(obj[prop], prop, obj);
        }
    }
};

//tests
var arr = [4, 5, 6];
var obj = {
    one: 1,
    two: 2,
    three: 3
};
myEach(arr, function(num) {
    console.log(num);
});
myEach(obj, function(num) {
    console.log(num);
});
myEach(obj, function(val, key) {
    console.log(key + ': ' + val);
});

//#############MAP#####################

var myMap = function(obj, callback) {
    var arr = [];
    if (typeof obj.length === 'number') {
        for (var i = 0; i < obj.length; i++)
            arr.push(callback(obj[i], i, obj));
    } else {
        for (var prop in obj) {
            arr.push(callback(obj[prop], prop, obj));
        }
    }
    return arr;
};

//tests

var arr = [100, 23, 33]; // 1 2 3
var obj = {
    one: 1,
    two: 2,
    three: 3
};
//one: 1 two: 2 three: 3
var obj2 = {
    title: 'Great Expectations',
    author: 'Charles Dickens'
};
var result = myMap(arr, function(num) {
    return num * 3;
});
console.log(result); //[ 300, 69, 99 ]
var result = myMap(obj, function(num) {
    return num * 3;
});
console.log(result); //[ 3, 6, 9 ]
var result = myMap(obj2, function(val, key) {
    return key + ': ' + val;
});
console.log(result); //[ 'title: Great Expectations', 'author: Charles Dickens' ]