Data Types
Objects and Arrays
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objects
collection of properties and methods
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creating a new object
new Object()
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creating a new object
(shortcut)
{}
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different ways to do
the same thing
var student = new Object();
student.name = 'John Doe';
student.age = 18;
var student = {name:'John Doe', age:18};
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keys can be strings
var student = {name:'John Doe', age:18};
var student = {'name':'John Doe', 'age':18};
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liberal formatting
var student = {name:'John Doe', age:18};
var student = {
name:'John Doe',
age:18
};
var student = {
name : 'John Doe',
age : 18
};
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writing properties
var student = {};
student.name = 'John Doe';
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write as many
as you want
var student = {};
student.name = 'John Doe';
student.age = 18;
student.gpa = 3.7;
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writing properties
(shortcut)
var student = {name:'John Doe'};
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writing multiple
properties
var student = {name:'John Doe', age:18, gpa:3.7};
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reading properties
var student = {name:'John Doe', age:18};
student.name // "John Doe"
student.age // 18
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reading properties
that are not set
var student = {name:'John Doe', age:18};
student.foobar // undefined
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different ways to do
the same thing
var student = {name:'John Doe', age:18};
student.name // "John Doe"
student['name'] // "John Doe"
student.age // 18
student['age'] // 18
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methods
we’ll cover them later
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arrays
ordered collection of values
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creating an array
new Array();
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new Array
with no arguments
var things = new Array();
things.length; // 0
creates empty array
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new Array
with one argument
var things = new Array(5);
things.length; // 5
creates array with number of undefined elements
shouldn’t ever need to do this, but be aware
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new Array
with multiple arguments
creates array with each
argument as element in array
var things = new Array(1,2,3);
things.length; // 3
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summary
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creating an array
(shortcut)
[]
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much more predictable
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array methods
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remember how strings
are zero indexed?
var car = "car";
car[0] // c
car[1] // a
car[2] // r
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arrays are too
var car = ['c', 'a', 'r'];
car[0] // c
car[1] // a
car[2] // r
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array of numbers
var things = [1,2,3,4,5];
things[0] // 1
things[1] // 2
things[2] // 3
things[3] // 4
things[4] // 5
things[5] // undefined
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remember how strings
know their length?
var football = "football";
football.length // 8
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arrays do too
var things = [1,2,3,4,5];
things.length // 5
http://www.w3schools.com/jsref/jsref_length_array.asp
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remember how strings can
get the indexOf stuff?
var football = "football";
football.indexOf('f') // 0
football.indexOf('o') // 1
football.indexOf('foot') // 0
football.indexOf('z') // -1
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arrays can too
var car = ['c','a','r'];
car.indexOf('c'); // 0
car.indexOf('a'); // 1
car.indexOf('r'); // 2
car.indexOf('b'); // -1
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more indexOf
examples
var strings = ['aa', 'b', 'ccD'];
strings.indexOf('aa') // 0
strings.indexOf('ccD') // 2
strings.indexOf('ccd') // -1
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arrays can be
multi-dimensional
var multi = ['a', 'b', ['z', 'y']];
multi[0] // 'a'
multi[1] // 'b'
multi[2] // ['z', 'y']
multi[2][0] // 'z'
multi[2][1] // 'y'
multi[2].length // 2
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concat
returns joined arrays but does not alter them
http://www.w3schools.com/jsref/jsref_concat_array.asp
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concat of a and b
var a = [1,2];
var b = [3,4];
var c = a.concat(b);
// a is still [1,2]
// b is still [3,4]
// c is now [1,2,3,4]
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concat of b and a
var a = [1,2];
var b = [3,4];
var c = b.concat(a);
// a is still [1,2]
// b is still [3,4]
// c is now [3,4,1,2]
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concat with
multi-dimensional
var multi = ['a', 'b', ['z', 'y']];
multi.concat([1, 2]) // ['a', 'b', ['z','y'], '1', '2']
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join
joins the elements of an array
into a string separated by a delimiter
http://www.w3schools.com/jsref/jsref_join.asp
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join
var car_letters = ['c', 'a', 'r'];
car_letters.join(''); // "car"
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join with delimiter
var car_letters = ['c', 'a', 'r'];
car_letters.join(','); // "c,a,r"
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delimiter can be any string
var car_letters = ['c', 'a', 'r'];
car_letters.join('WIN'); // "cWINaWINr"
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date example
var date = [9, 8, 2009]
date.join('/'); // "9/8/2009"
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string has the opposite
of join called split
var date = "9/8/2009"
date.split('/') // [‘9’,‘8’,‘2009’]
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split/join allow for
switching back and forth
var date = "9/8/2009";
var date_array = date.split('/') // [‘9’,‘8’,‘2009’]
var date_string = date_array.join('/'); // “9/8/2009”
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reverse
reverses the order of an array
http://www.w3schools.com/jsref/jsref_reverse.asp
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reverse
var car = ['r', 'a', 'c'];
car.reverse(); // ['c', 'a', 'r']
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sort
sorts the elements of an array
http://www.w3schools.com/jsref/jsref_sort.asp
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sorting numbers
var numbers = [5,3,99,77,2];
numbers.sort(); // [2,3,5,77,99]
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sorting strings
var names = ['John', 'Steph', 'Steve', 'Carrie'];
names.sort(); // ['Carrie','John','Steph','Steve']
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upper case before
lower case
var letters = ['a', 'B', 'c', 'D'];
letters.sort(); // ['B','D','a','c']
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pop
removes and returns the last element of an array
(opposite of shift)
http://www.w3schools.com/jsref/jsref_pop.asp
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pop
var car = ['c', 'a', 'r'];
var last = car.pop();
last // 'r'
car // ['c','a']
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pop
var car = ['c', 'a', 'r'];
car.pop(); // 'r'
car.pop(); // 'a'
car.pop(); // 'c'
car.pop(); // undefined
car.length // 0
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shift
removes and returns the first element of an array
(opposite of pop)
http://www.w3schools.com/jsref/jsref_shift.asp
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shift
var car = ['c', 'a', 'r'];
var first = car.shift();
first // 'c'
car // ['a','r']
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shift
var car = ['c', 'a', 'r'];
car.shift(); // 'c'
car.shift(); // 'a'
car.shift(); // 'r'
car.shift(); // undefined
car.length // 0
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push
adds one or more elements to the end of
an array and returns the new length
(opposite of unshift)
http://www.w3schools.com/jsref/jsref_push.asp
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push single element
var car = ['c','a','r'];
car.push('d'); // 4
car // ['c','a','r','d']
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push multiple elements
var car = ['c','a','r'];
car.push('d', 'e', 'd'); // 6
car // ['c','a','r','d', 'e', 'd']
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unshift
adds one or more elements to the beginning of the
array and returns the new length (opposite of push)
http://www.w3schools.com/jsref/jsref_unshift.asp
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unshift single element
var car = ['c','a','r'];
car.unshift('s'); // 4
car // ['s','c','a','r']
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unshift multiple
elements
var car = ['c','a','r'];
car.unshift('o', 's'); // 5
car // ['o','s','c','a','r']
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shift/unshift pop/push
end of array
beginning of array
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slice
slices elements out of an array without changing array
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slice parameters
array.slice(starting position, index after last position)
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slice with one argument
var numbers = [1,2,3,4];
numbers.slice(2); // [3, 4]
numbers // [1,2,3,4]
slices from index to end of array
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slice with two
arguments
slices from beginning index to
index before second argument
var numbers = [1,2,3,4];
numbers.slice(0, 2); // [1, 2]
numbers // [1,2,3,4]
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slice with negative
second argument
var numbers = [1,2,3,4];
numbers.slice(1, -1); // [2, 3]
numbers.slice(1, -2); // [2]
numbers // [1,2,3,4]
negative starts from end and goes backwards
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splice
adds and removes elements from an array
http://www.w3schools.com/jsref/jsref_splice.asp
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splice parameters
array.splice(index, how many to remove, elements to add)
index and how many to remove are required
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removing an element
from an array
var letters = ['a', 'c', 'd'];
letters.splice(1, 1); // 'c'
letters // ['a','d']
in english: at index 1, remove 1 element
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removing multiple
elements from an array
var letters = ['a', 'c', 'd'];
letters.splice(1, 2); // ['c','d']
letters // ['a']
in english: at index 1, remove 2 elements
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adding an element
to an array
var letters = ['a', 'c', 'd'];
letters.splice(1, 0, 'b'); // ['a', 'b', 'c', 'd']
in english: at index 1, remove 0 elements, add ‘b’
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adding multiple
elements to an array
in english: at index 1, remove 0 elements,
add ‘b’ and ‘c’
var letters = ['a', 'c', 'd'];
letters.splice(1, 0, 'b', 'c');
letters // ['a','b','c','c','d']
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replacing elements
in an array
var car = ['c', 'a', 'r'];
car.splice(0, 1, 'b'); // 'c'
car // ['b','a','r']
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var person = {name:'John Doe'};
person.name
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var person = {name:'John Doe'};
person.name
'John Doe'
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var person = {name:'John Doe'};
person.name = 'Jane Doe';
person.name
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var person = {name:'John Doe'};
person.name = 'Jane Doe';
person.name
'Jane Doe'
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var person = {name:'John Doe'};
person['name']
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var person = {name:'John Doe'};
person['name']
'John Doe'
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[12, 23, 36].length
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[12, 23, 36].length
3
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[12, 23, 36].indexOf(12)
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[12, 23, 36].indexOf(12)
0
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[12, 23, 36].indexOf(35)
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[12, 23, 36].indexOf(35)
-1
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['b','a','t'].join('')
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['b','a','t'].join('')
'bat'
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'9/8/2009'.split('/')
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'9/8/2009'.split('/')
['9', '8', '2009']
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var numbers = [1,2,3];
numbers.push(4)
numbers
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var numbers = [1,2,3];
numbers.push(4)
numbers
[1,2,3,4]
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var numbers = [1,2,3,4];
numbers.shift();
numbers
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var numbers = [1,2,3,4];
numbers.shift();
numbers
[2,3,4]
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var numbers = [2,3,4];
numbers.unshift(1);
numbers
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var numbers = [2,3,4];
numbers.unshift(1);
numbers
[1,2,3,4]
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var numbers = [2,3,4];
numbers.pop();
numbers
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var numbers = [2,3,4];
numbers.pop();
numbers
[2,3]
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var numbers = [2,3,4];
numbers.splice(1, 0, 1);
numbers
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var numbers = [2,3,4];
numbers.splice(1, 0, 1);
numbers
[2,1,3,4]
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var numbers = [2,3,4];
numbers.splice(0, 1, 1);
numbers
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var numbers = [2,3,4];
numbers.splice(0, 1, 1);
numbers
[1,3,4]
Tuesday, September 8, 2009