Your SlideShare is downloading. ×
Java Script Introduction
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Java Script Introduction

3,150
views

Published on

sdhjl2000@gmail.com

sdhjl2000@gmail.com

Published in: Technology

0 Comments
7 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total Views
3,150
On Slideshare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
117
Comments
0
Likes
7
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. JavaScript Introduction Aaron Conran Text: JavaScript The Definitive Guide By David Flannagan
  • 2. Case Sensitive
    • Example:
    • myVar
    • myVAr
    • These are not the same variable.
  • 3. (Optional) Semicolons
    • JavaScript allows you to omit semicolons at the end of your statements.
    • However this can create nasty bugs and cause difficult to debug problems.
    • Use them at the end of statements and make your life easier.
  • 4. Comments
    • JavaScript supports both C and C++ style comments
    • // this is a comment
    • /* this is another comment */
  • 5. Comments (JSDoc)
    • Comments which begin with /**
    • Note the 2 stars will be picked up by JSDoc
    • JSDoc allows you to document your JavaScript classes in a formal manner similar to JavaDoc.
    • Allows code and documentation to always be synchronized.
    • For more information:
    • http://jsdoc.sourceforge.net/
  • 6. JavaScript Reserved Words
    • Avoid the use of reserved words as variables and function names in your JavaScript.
    • For a full list
    • Flanagan p19-20
    • Examples:
      • break
      • if
      • switch
      • in
      • class
  • 7. JavaScript DataTypes
    • Numbers
    • Strings
    • Booleans
    • Functions
    • Objects
    • Arrays
    • null
    • undefined
    • Date
    • Error
  • 8. Numbers
    • Integer (whole)
    • Hexadecimal & Octal
    • Floating-points (decimal)
    • You can add, multiply divide and subtract numbers with their respective operator: +, *, /, & -
    • The Math library of JavaScript also exposes a number of useful methods:
      • Math.abs(num)
      • Math.sin(num)
      • Math.ceil(num)
      • Full reference p 659-669
  • 9. Special Numeric Values (Table 3-1) p25 Special value to represent negative infinity Number.NEGATIVE_INFINITY Special value to represent infinity Number.POSTIVE_INFINITY Special not a number value Number.NaN Smallest (closest to zero) representable number Number.MIN_VALUE Largest representable number Number.MAX_VALUE Special not-a-number value NaN Special value to represent infinity Infinity Meaning Constant
  • 10. Strings
    • “ zero or more Unicode characters enclosed within single or double quotes”
    • Examples:
      • “”
      • ‘ myForm’
      • “ testing”
      • “ This is a longer string”
  • 11. Escape Sequences
    • To encode special values like new lines and ‘s in JavaScript strings you utilize a backslash
    • Example:
      • var menuText = ‘What’s this?’;
  • 12. Escape Sequences (Table 3-2) p27 The Latin-1 character specified by the octal digits XXX, between 1 and 377. Not support by ECMAScript v3; do not use this escpae sequence. XXX The Unicode character specified by the four hexadecimal digits XXXX uXXXX The Latin-1 character specified by the two hexadecimal digits XX xXX Backslash (u005C) Apostrophe or single quote (u027) ’ Double quote (u022) ” Carriage return (u00D) Form feed (u000C) f Vertical tab (u000B) v Newline (u000A) Horizontal tab (u0009) Backspace (u0008)  The NUL character (u0000) Character represented Sequence
  • 13. Adding Strings
    • You can also add (or concatenate) strings simply by adding them.
    • Example:
    • var anotherString = ‘new’;
    • var newVariable = ‘Something ‘ + anotherString;
    • When adding numbers they will automatically be converting to strings.
    • Example:
    • var x = 12;
    • var newString = x + ‘ dozen eggs’;
  • 14. Converting Strings To Numbers
    • Utilize the parse Number utility functions to extract numbers from strings.
      • parseInt
      • parseFloat
    • Example:
    • var x = “11”;
    • var xNum = parseInt(x);
  • 15. Booleans
    • true
    • (Other truthy values)
    • 1
    • {}
    • ‘ ‘ - space
    • ‘ my String’
    • false
    • (Other falsey values)
    • undefined
    • null
    • 0
    • “” – empty string
  • 16. Equals vs Strictly Equals
    • There is a strictly equals operator in JavaScript which will also check type as well as value. To show how this relates to boolean values:
    • == Equals
      • Works for Truthy values
    • === Strictly Equals
      • Works for truth only
    • != Not Equals
      • Works for Falsey values
    • !== Strictly Not Equals
      • Works for false only
  • 17. Objects
    • JavaScript Objects are similar to ColdFusion Structures.
    • They consist of zero to many key-value pairs.
    • They can be nested infinitely deep.
    • They provide an associative array or hash map.
    • Example:
    • // using the Object constructor
    • var newObj = new Object();
    • newObj.x = 10;
    • newObj.y = 20;
    • // OR using the Object literal syntax
    • var newObj = {x: 10, y: 20};
  • 18. Object Literal
    • Object literal is the preferred way to create objects because it is concise and consistent with JSON-syntax.
    • When utilizing object literal syntax key value pairs are separated by colon’s.
    • Keys are called properties
  • 19. Functions
    • Functions are actually a datatype too
    • Example:
    • var myFn = function() {console.log(‘hi’);};
    • function myFn() {console.log(‘hi’);}
    • These are 2 different ways of defining a similar function. There is also a Function constructor, however it’s use is limited because it can only create functions in the global scope.
  • 20. Functions as Properties
    • Properties of Objects can be any data type including Functions.
    • Example:
    • var myObject = {myFun: function() {console.log(‘hi’);}};
    • myObject.myFun();
  • 21. Arrays
    • Arrays can be defined using 2 syntaxes as well.
    • Example:
    • // Utilizing the Array constructor
    • var myArray = new Array();
    • myArray[0] = 12;
    • myArray[1] = 232;
    • // OR using the Array literal syntax.
    • var myArray = [12,232];
  • 22. Arrays (cont.)
    • Arrays can be infinitely nested
    • Arrays can be sparse
    • Arrays can store unlike datatypes
    • Full reference available p 602-611
    • Arrays provide a number of useful properties and methods such as:
      • length – property which defines how many elements are in the Array
      • push – method which pushes another element on the Array when utilized as a Stack
      • pop – method which pops an element off an Array when utilized as a Stack
  • 23. null vs undefined
    • null
    • “ null is a special keyword which indicates no value”
    • undefined
    • “ undefined is returned when you use either a variable that has not been declared but never had a value assigned to it or an object property that does not exist”
  • 24. null vs undefined
    • Both of these equate to a falsey value.
    • var myVar;
    • // what is the value of myVar?