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Java versus JavaScript versus HTML Issues
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Some Simple Motivating Examples
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Language Features and Syntax
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The Peculiar Object Model -- Functions Properties and Methods
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Arrays in old and new JavaScript
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Arguments of Functions
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with and other object related syntax
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The JavaScript built in Math String and Date Objects
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The Navigator Objects -- Frames Windows Document Form
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Event Handling including Function object
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Cookies
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User Objects and Examples including using JavaScript for frames
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Historically JavaScript was called LiveScript and developed by Netscape with some of the same goals as Java but focussed on a "smaller world" -- manipulation of text and options connected with Netscape Clients
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TEXT ............................................. COMPUTER Language
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HTML --> JavaScript Java <--- C++
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Now we can use it under some circumstances as an alternative to Java where the "rapid prototyping" of a fully scripted language is helpful
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We expect somebody to develop a fully interpreted Java -- equivalently to extend JavaScript to support more built-in objects (e.g. networking, images)
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JavaScript is "either" active text (HTML) or a focused language!
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JavaScript can be thought of as Java with the AWT (Abstract Windowing Toolkit) replaced by Netscape Client
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JavaScript is a domain specific Interpreter for "Web Document Domain"
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e.g. Postscript is a domain specific Interpreter for text layout and MATLAB is an interpreter for matrix manipulation, Mathematica is domain specific for mathematics ......
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Execute C code Instruction -- 1 clock cycle ( 10^8 per second)
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Run a client side C subroutine -- can do upto 10^6 instructions in time (few milliseconds) that is significant for user
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JavaVM Interpreter -- roughly 50 times slower than C
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JavaVM Just in Time Compiler (effectively compile JavaVM in real time) -- roughly 2 to 8 times slower than C
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Native Java Compiler -- same speed as C
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Perl Interpreter (but does process whole program before interpreting) -- 500 times slower than C except in runtime
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Tcl, JavaScript "true" Interpreters - 5000 times slower than C
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Can still do 100-1000 instructions in time that users don't notice!
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Contact Host via CGI script -- Server, Network and Client HTML page regeneration delay can be measured in seconds.
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Abstract * Foil Index for this file
Secs 48.9
See also color IMAGE
