Pemrograman Berbasis Web10 – Java Script (3)

Informatics DepartmentParahyangan Catholic University

Array’s Method (contd.)

Shifting Elements works like popping an element, but

instead of removing the last element, shift() method removes the first element and shifts all other elements forward.

works like dequeue in Queue data structure

Example:var fruits = ["Banana", "Orange", "Apple", "Mango"];var removed = fruits.shift(); //fruits = ["Orange", "Apple", "Mango"]//removed = “Banana”

Array’s Method (contd.)

Unshifting Elements The unshift() method adds a new

element at the beginning of an array and shifts the old elements backward

Example:var fruits = ["Banana", "Orange", "Apple", "Mango"];fruits.unshift("Lemon");    //fruits = ["Lemon", "Banana", "Orange", "Apple", "Mango"]

Array’s Method (contd.)

Deleting Elements Changes an element to undefined This leaves a “hole” in an array

Example:var fruits = ["Banana", "Orange", "Apple", "Mango"];delete fruits[1];//fruits = ["Banana", undefined, "Apple", "Mango"]

Array’s Method (contd.)

Splicing an Array The splice() method can be used to add

new items or remove some items to/from an array

Example:var fruits = ["Banana", "Orange", "Apple", "Mango"];fruits.splice(2, 1, "Lemon", "Kiwi");//fruits = ["Banana", "Orange",  "Lemon", "Kiwi", "Mango"]

where to splice

how many elements should be removed

new elements to be inserted

Array’s Method (contd.)

Slicing an Array The slice() method slices out a piece of

an array into a new array

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

starting indexending index (not included in the result)

Array’s Method (contd.)

Searching in an Array The indexOf() method searches the

array for an element and return its position (first to be found)

The lastIndexOf() method searches the array for and element, starting at the end, and returns its position

Example:var foo = ["H", "E", "L", "L", "O"];var firstL = foo.indexOf("L"); //2var lastL = foo.lastIndexOf("L"); //3

Regular Expression

A regular expression is a sequence of characters that forms a search pattern.

The search pattern can be used for text search and text replace operations.

Regular Expression

Syntax: /pattern/modifiers;

Example:

w3school is a pattern (to be used in search) i is a modifier (modifies the search to be case-

insensitive)

var patt = /w3schools/i;

Regular Expression

In Java Script, RE usually used for search() and replace() string methods

Example:var str = "Visit W3Schools";var n = str.search(/w3schools/i); //n = 6

var str = "Visit W3Schools!";var n = str.search("W3Schools"); //n = 6

var str = "Visit W3Schools!";var n = str.search(“w3schools"); //n = -1

Regular Expression

Example:var str = "Visit Microsoft!";var res = str.replace(/microsoft/i, "W3Schools");//res = "Visit W3Schools!"var str = "Visit Microsoft!";var res = str.replace("Microsoft", "W3Schools");//res = "Visit W3Schools!"var str = "Visit Microsoft!";var res = str.replace(”microsoft", "W3Schools");//res = "Visit Microsoft!"

Regular Expression

Modifiers i

perform case-insensitive matching g

perform a global match (find all the matches rather than stopping after the first match)

mperform multiline matching (find first occurrences in every line)

Regular Expression

Patterns:Brackets are used to find a range of characters [abc]

find any characters which is a, b or c [^abc]

find any characters which is not a, not b, and not c

[a-z]find any characters between a and z (inclusive)

[^a-z]find any characters which is not a, b, ... , z (inclusive)

Regular Expression

Quantifiers: n+

matches any string that contains at least one n

n*matches any string that contains zero or more occurrences of n

n?matches any string that contains zero or one occurrences of n

Regular Expression

The test() method is a RE method. It searches a string for a pattern, and returns true or false, depending on the result.

Example:var patt = /free/;patt.test("The best things in life are free!");//returns true since the string has “free” in itvar patt = /frees/;patt.test("The best things in life are free!");//returns false since the string doesn’t has “frees” in it

Regular Expression

Example:var patt = /frees*/;patt.test("The best things in life are free!");//returns true since the string has “free” in it. Note that s* means zero s is permitable

var patt = /frees+/;patt.test("The best things in life are free!");//returns false since the string has “frees” in itvar patt = /fre?!/;patt.test("The best things in life are free!");//returns false since e?! means zero or one e then followed by a “!”. In this string there is 2 “e”s