JavaScript
JavaScript and Events
JavaScript event handlers
| Event Handler | What Caused It |
| onAbort | Image loading was interrupted. |
| onBlur | The user moved away from a form element. |
| onChange | The user changed a value in a form element. |
| onClick | The user clicked on a button-like form element. |
| onError | The program had an error when loading an image. |
| onFocus | The user activated a form element. |
| onLoad | The document finished loading. |
| onMouseOut | The mouse moved away from an object. |
| onMouseOver | The mouse moved over an object. |
| onSubmit | The user submitted a form. |
| onUnLoad | The user left the window or frame. |
JavaScript and JScript
JavaScript and JScript
| JavaScript or JScript Version | Browsers Supported |
| JavaScript 1.0 | Netscape Navigator 2.0, Internet Explorer 3.0 |
| JavaScript 1.1 | Netscape Navigator 3.0, Internet Explorer 4.0 |
| JavaScript 1.2 | Netscape Navigator 4.0–4.05, Internet Explorer 4.0 |
| JavaScript 1.3 | Netscape Navigator 4.06–4.7x, Internet Explorer 5.0 |
| JavaScript 1.5 | Netscape Navigator 6.0+, Mozilla (open source browser), Internet Explorer 5.5+ |
| JScript 1.0 | Internet Explorer 3 |
| JScript 2.0 | Internet Explorer 3 |
| JScript 3.0 | Internet Explorer 4 |
| JScript 4.0 | Internet Explorer 4 |
| JScript 5.0 | Internet Explorer 5 |
| JScript 5.5 | Internet Explorer 5 |
| JavaScript is supported by Netscape 2, Explorer 3, Opera 3, and all newer versions of these browsers. In addition, HotJava 3 supports JavaScript, as do iCab for the Mac, WebTV, OmniWeb for OS X, QNX Voyager and Konqueror for the Linux KDE environment. NetBox for TV, AWeb and Voyager 3 for Amiga, and SEGA Dreamcast and ANT Fresco on RISC OS also support JavaScript.
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Reserved keywords
Reserved keywords
| abstract | boolean | break | byte | case | catch |
| char | class | const | continue | default | delete |
| do | double | else | extends | false | final |
| finally | float | for | function | goto | if |
| implements | import | in | instanceof | int | interface |
| long | native | new | null | package | private |
| protected | public | return | short | static | super |
| switch | synchronized | this | throw | throws | transient |
| true | try | typeof | var | void | volatile |
| while | with |
Data Types
- Primitive Data Types
Primitive data types are the simplest building blocks of a program. They are types that can be assigned a single literal value such as the number 5.7, or a string of characters such as "hello". JavaScript supports three core or basic data types:
- numeric
- string
- Boolean
In addition to the three core data types, there are two other special types that consist of a single value:
- null
- undefined
- Composite Data Types
Escape Sequence
Reserved keywords
| Escape Sequence | What It Represents |
| \' | Single quotation mark |
| \" | Double quotation mark |
| \t | Tab |
| \n | Newline |
| \r | Return |
| \f | Form feed |
| \b | Backspace |
| \e | Escape |
| \\ | Backslash |
Variables
Variables are fundamental to all programming languages. They are data items that represent a memory storage location in the computer. Variables are containers that hold data such as numbers and strings. Variables have a name, a type, and a value.
num = 5; // name is "num", value is 5, type is numeric
friend = "Peter"; // name is "friend", value is "Peter", type is string
How JavaScript converts datatypes
How JavaScript converts datatypes
Variable Assignment Conversion
var item = 5.5; Assigned a float
item = 44; Converted to integer
item = "Today was bummer"; Converted to string
item = true; Converted to Boolean
item = null; Converted to the null value