Object Oriented and Functional Programming

constructor

var Car = function(wheels, seats, engines) {
  //Change this constructor
  this.wheels = wheels;
  this.seats = seats;
  this.engines = engines;
};

public & private

public: this

private: var

var Car = function() {
  // this is a private variable
  var speed = 10;

  // these are public methods
  this.accelerate = function(change) {
    speed += change;
  };

  this.decelerate = function() {
    speed -= 5;
  };

  this.getSpeed = function() {
    return speed;
  };
};

functional programming

.map() ---> Iterate over array and return new array

var newArray = oldArray.map(function(val) {
  return val + 3;
});

• .map() iterate array to get array each element val

• callback function take val as parameter and add 3 to every value and save results in newArray

• instead of val, can callback parameter can also include index and array being acted on.

.reduce() ---> Iterate over array and condense it into one value

singleVal = array.reduce(function(preVal, curVal){
  return preVal + curVal;
}, 0);

• .reduce() iterate array to get each element curVal and keep accumulator preVal
• second para of .reduce() is the initial val of accumulator
• sum all values of old array and return it.

.filter() ---> Iterate array and filter out elements where don't meet condition

array = array.filter(function(val) {
  return val !== 5;
});

• .filter() iterate array to get each element val
• callback take val as para when keep that element when it returns true, otherwise filters it out.
• remove array elements that are equal to five and return a new array

.sort() ---> Iterate array and sort it

array.sort(function(a, b) {
  return a - b;
});

• sort from smallest to largest

• .sort() iterate array to get each element a and the next of it b

• callback is a compare function:

  • a before b ---> return <0
  • a after b ---> return >0
  • a equal b ---> return 0

• sort alphabetically if no callback

• the original array will be altered

.reverse() ---> reverse array

newArray = array.reverse();

• simple as it looks like
• original array will be altered

.concat() ---> Concatenate array

newArray = oldArray.concat(otherArray);

• return new array

.split() ---> split string into array

array = string.split(' ');

• argument is delimiter

.join() ---> join array element into a string

var veggies = ["Celery", "Radish", "Carrot", "Potato"];
var salad = veggies.join(" and ");
console.log(salad); // "Celery and Radish and Carrot and Potato"

• argument is delimiter

.replace() ---> replace a specified value in string

//remove all non-alphanumeric char from a str
str = str.replace(/[^0-9a-z]/gi, '');

• 1st arg is search value/ regular expression; 2nd arg is replacement value

• original string does not change

.substr(start [,length]) ---> extracts parts of a string

var str = "Hello world!";
var res = str.substr(11, 1); // "!"
var res = str.substr(2); // "llo world!"

• original string does not change

.slice(start [,end]) ---> extracts parts of a string/array

var str = "Hello world!";
var res = str.slice(3); // "lo world!"
var res = str.slice(3, 8); // "lo wo"
var res = str.slice(-1); // "!"

var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
var citrus = fruits.slice(1, 3); // ["Orange", "Lemon"]

• select parts from the start and ends at, but does not include, the given end argument.

• new string/array will be returned

.indexOf(item [,start]) ---> returns index of item in string/array

var str = "Hello world, welcome to the universe.";
var n = str.indexOf("e"); // 1
var n = str.indexOf("e", 5); // 14

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var a = fruits.indexOf("Apple"); //2
var a = fruits.indexOf("Apple", 4); // 6

• return -1 when item no found

charCodeAt() ---> returns the unicode of the character at a specified index in a string

var str = "HELLO WORLD";
str.charCodeAt(0); // 72

• some common unicode
  • 0 - 9 : 48 - 57
  • A - Z : 65 - 90
  • a - z : 97 - 122

String.fromCharCode(n1 [, n2, ..., nX]) ---> converts Unicode values into characters.

var res = String.fromCharCode(72, 69, 76, 76, 79); // "HELLO"

• static method, always be used in form String.fromCharCode()