Advanced Array Methods(map)

map

: Creates a new array

  Iterates through an array

  Runs a callback function for each value in the array

  Adds the result of that callback function to the new array

  Returns the new array

function map(array, callback){

var newArr = [];

for(var i = 0; i < array.length; i++){

newArr.push(callback(array[i], i, array));

}

return newArr;

}

/*

Write a function called doubleValues which accepts an array and returns a new array with all the values in the array passed to the function doubled

Examples:

    doubleValues([1,2,3]) // [2,4,6]

    doubleValues([1,-2,-3]) // [2,-4,-6]

*/

function doubleValues(arr){

    var newArr = [];                                                  

    arr.map(function(val, i, arr){                                 >            return arr.map(function(val){

        return val * 2;                                                    

    })                                                                       });

}                                                                           }

/*

Write a function called valTimesIndex which accepts an array and returns a new array with each value multiplied by the index it is currently at in the array.

Examples:

    valTimesIndex([1,2,3]) // [0,2,6]

    valTimesIndex([1,-2,-3]) // [0,-2,-6]

*/

function valTimesIndex(arr){

    return arr.map(function(val, i , arr){ 

        return val * i;

    })

}

/*

Write a function called extractKey which accepts an array of objects and some key and returns a new array with the value of that key in each object.

Examples:

    extractKey([{name: 'Elie'}, {name: 'Tim'}, {name: 'Matt'}, {name: 'Colt'}], 'name') // ['Elie', 'Tim', 'Matt', 'Colt']

*/

function extractKey(arr, key){

    return arr.map(function(val){

        return val[key];

    })

}

/*

Write a function called extractFullName which accepts an array of objects and returns a new array with the value of the key with a name of "first" and the value of a key with the name of  "last" in each object, concatenated together with a space. 

Examples:

    extractFullName([{first: 'Elie', last:"Schoppik"}, {first: 'Tim', last:"Garcia"}, {first: 'Matt', last:"Lane"}, {first: 'Colt', last:"Steele"}]) // ['Elie Schoppik', 'Tim Garcia', 'Matt Lane', 'Colt Steele']

*/

function extractFullName(arr, key){

    return arr.map(function(val){

        return val[key]                                    >            return val.first + " " + val.last;

    })

}