[PDF] Introduction to JavaScript - cglabca

Javascript: Objects, and Functions

Like Perl and Ruby, Javascript already have operations for pushing and popping an array from both ends, so one can use push and shift functions to enqueue and dequeue a list (or, in reverse, one can use unshift and pop) • A two-dimensional array in JavaScript is an array of arrays

javascript builtin functionshtm Copyright © tutorialspoint

the range in which JavaScript normally uses standard notation toFixed Formats a number with a specific number of digits to the right of the decimal toLocaleString Returns a string value version of the current number in a format that may vary according to a browser's locale settings

Beginner’s essential JavaScript Cheat Sheet

JavaScript Basics 3 Variables in JavaScript 3 The Next Level: Arrays 4 Operators 5 Functions 6 JavaScript Loop 7 If - Else Statements 8 Strings 8 Regular Expression Syntax 9 Numbers and Math 11 Dealing with Dates in JavaScript 13 DOM Mode 14 Working with the User Browser 17 JavaScript Events 19 2 of 24

Introduction to JavaScript - cglabca

What can JavaScript Do? • JavaScript can dynamically modify an HTML page • JavaScript can react to user input • JavaScript can validate user input • JavaScript can be used to create cookies (yum) • JavaScript is a full-featured programming language • JavaScript user interaction does not require any communication with the server

JavaScript the Hard Parts - Frontend Masters

Sep 18, 2019 · - Closure is the most esoteric of JavaScript concepts - Enables powerful pro-level functions like ‘once’ and ‘memoize’ - Many JavaScript design patterns including the module pattern use closure - Build iterators, handle partial application and maintain state in an asynchronous world

Ch5 - Le Langage JavaScript

A 4 Utilisation de fonctions JavaScript et gestionnaires d’événements A 4 1 Gestion des événements Les fonctions de JavaScript permettent de lancer des actions spécifiques (plusieurs fois de suite ou plusieurs fonctions différentes) dans une même page Pour ce faire on les associe souvent à des gestionnaires d’événements

Using JavaScript with Twine - Code Liberation

Lecture 1b: Using JavaScript with Twine The Code Liberation Foundation What is jQuery? A JavaScript framework, or set of pre-made tools and functions jQuery makes creating animation, interaction effects, etc using JavaScript easier

Designer Scripting Basics - Adobe Inc

May 24, 2016 · JavaScript, a powerful scripting language, provides you with a great deal of flexibility when creating your scripts and allows you to leverage any existing knowledge of the language

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Introduction to JavaScriptPat MorinCOMP2405

2Outline•What is JavaScript?-History-Uses•Adding JavaScript to HTML•JavaScript syntax•JavaScript events•JavaScript classes•The HTML Document Object Model

3What is JavaScript?•JavaScript is a programming language for use in HTML pages•Invented in 1995 at Netscape Corporation (LiveScript)•JavaScript has nothing to do with Java•JavaScript programs are run by an interpreter built into the user's web browser (not on the server)

4Where does JavaScript Fit In?•Recall1.client opens connection to server2.client sends request to server3.server sends response to client4.client and server close connection•What about Step 5?5.Client renders (displays) the response received from server•Step 5 involves displaying HTML•And running any JavaScript code within the HTML

5What can JavaScript Do?•JavaScript can dynamically modify an HTML page•JavaScript can react to user input•JavaScript can validate user input•JavaScript can be used to create cookies (yum!)•JavaScript is a full-featured programming language•JavaScript user interaction does not require any communication with the server

6Pros and Cons of JavaScript•Pros:-Allows more dynamic HTML pages, even complete web applications•Cons:-Requires a JavaScript-enabled browser-Requires a client who trusts the server enough to run the code the server provides•JavaScript has some protection in place but can still cause security problems for clients-Remember JavaScript was invented in 1995 and web-browsers have changed a lot since then

7Using JavaScript in your HTML•JavaScript can be inserted into documents by using the SCRIPT tag

8Where to Put your Scripts•You can have any number of scripts•Scripts can be placed in the HEAD or in the BODY-In the HEAD, scripts are run before the page is displayed-In the BODY, scripts are run as the page is displayed•In the HEAD is the right place to define functions and variables that are used by scripts within the BODY

9Using JavaScript in your HTML

10External Scripts•Scripts can also be loaded from an external file•This is useful if you have a complicated script or set of subroutines that are used in several different documents

11JavaScript Variables•JavaScript has variables that you can declare with the optional var keyword•Variables declared within a function are local to that function•Variables declared outside of any function are global variablesvar myname = "Pat Morin";

12JavaScript Operators and Constructs•JavaScript has most of the operators we're used to from C/Java-Arithmetic (+, - , *, /, %)

-Assignment (=, +=, -=, *= /=, %=, ++, --) -Logical (&&, ||, !) -Comparison (<, >, <=, >=, ==) •Note: + also does string concatentation•Constructs: -if, else, while, for, switch, case

13Simple User Interaction•There are three built-in methods of doing simple user interaction-alert(msg) alerts the user that something has happened-confirm(msg) asks the user to confirm (or cancel) something-prompt(msg, default) asks the user to enter some textalert("There's a monster on the wing!");confirm("Are you sure you want to do that?");prompt("Enter you name", "Adam");

14JavaScript Functions•JavaScript lets you define functions using the function keyword•Functions can return values using the return

keywordfunction showConfirm() { confirm("Are you sure you want to do that?");}

15JavaScript Arrays•JavaScript has arrays that are indexed starting at 0•Special version of for works with arrays

16JavaScript Events•JavaScript can be made to respond to user events•Common Events:-onload and onunload : when a page is first visited or left-onfocus, onblur, onchange : events pertaining to form elements-onsubmit : when a form is submitted-onmouseover, onmouseout : for "menu effects"•A complete list of event types is available here-http://www.w3schools.com/jsref/jsref_events.asp

17Exception Handling•JavaScript also has try, catch, and throw

keywords for handling JavaScript errorstry { runSomeCode();} catch(err) { var txt="There was an error on this page.\n\n" + "Error description: " + err.description + "\n\n" alert(txt)}

18Comments in JavaScript•Comments in JavaScript are delimited with // and /* */ as in Java and C++

19JavaScript Objects•JavaScript is object-oriented and uses the same method-calling syntax as Java•We have already seen this with the document

objectdocument.write("Hello World!");

20Built-In JavaScript Objects•Some basic objects are built-in to JavaScript-String-Date-Array-Boolean-Math

21JavaScript Strings•A String object is created every time you use a string literal (just like in Java)•Have many of the same methods as in Java-charAt, concat, indexOf, lastIndexOf, match, replace, search, slice, split, substr, substring, toLowerCase, toUpperCase, valueOf•There are also some HTML specific methods-big, blink, bold, fixed, fontcolor, fontsize, italics, link, small, strike, sub, sup•Don't use the HTML methods (use CSS instead)-This is the worst kind of visual formatting

22JavaScript Dates•The Date class makes working with dates easier•A new date is initialized with the current date•Dates can be compared and incrementedvar myDate = new Date();myDate.setFullYear(2007,2,14);var today = new Date();var nextWeek = today + 7;if (nextWeek > today) { alert("You have less than one week left");}

23JavaScript Arrays and Booleans•We have already seen the Array class•The Boolean class encapsulates a boolean value

24The JavaScript Math Class•The Math class encapsulates many commonly-used mathematical entities and formulas•These are all class methods-abs, acos, asin, atan, atan2, ceil, cos, exp, floor, log, max, min, pow, random, round, sin, sqrt, tan•These are all class methods-E, LN2, LN10, LOG2E, LOG10E, PI, SQRT1_2, SQRT2if (Math.cos(Math.PI) != 0) { alert("Something is wrong with Math.cos");}

25JavaScript and the DOM•The Document Object Model (DOM) is a specification that determines a mapping between programming language objects and the elements of an HTML document•Not specific to JavaScript

26HTML DOM Objects•Environment objects-Window, Navigator, Screen, History, Location, Document•HTML objects-Anchor, Area, Base, Body, Button, Event, Form, Frame, Frameset, Iframe, Image, Checkbox, FileUpload, Hidden, Password, Radio, Reset, Submit, Text, Link, Meta, Object, Option, Select, Style, Table, TableCell, TableRow, TextArea

27HTML DOM: Document•The Document object represents an HTML document and can be used to access all documents in a page•A Document contains several collections-anchors, forms, images, links•Has several properties-body, cookie, domain, lastModified, referrer, title, URL•Has several useful methods-getElementById, getElementsByName, getElementsByTagName, write, writeln, open, close

28HTML DOM: Document•An instance of Document is already created for you, called documentfunction changeF() { var cText = document.getElementById("c"); var fText = document.getElementById("f"); ...}

...CF

29HTML DOM: Form Elements•One of the most common uses of JavaScript is for form validation•Several HTML DOM classes encapsulate form elements-Form, Button, Checkbox, Hidden, Password, Text, Radio, Reset, Submit, Textarea•Warning: Using JavaScript is not a substitute for validating form data in CGI scripts

30HTML DOM: Text•A text entry field (input type="text") is encapsulated by a Text object•Variables-value, maxLength, id, size, name, tabindex, readOnly•Changing these variables has an immediate effect on the displayed data

31HTML DOM: The Document Tree•Accessing elements and changing their properties lets us do simple things like form validation, data transfer etc•HTML DOM lets us do much more•We can create, delete, and modify parts of the HTML document•For this we need to understand the Document Tree

32HTML DOM: The Document Tree

33Navigating the Document Tree•With JavaScript we can navigate the document tree•document.getElementById(), getElementsByName(), and getElementsByTagName() return nodes in the document tree•Information can be obtained from-nodeName - The tag name-nodeValue - The the text of a text node-nodeType - The kind of node

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