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Console
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Two key uses Error Messages Print Stmts If you see an error message
Don’t panic Use it to help Like validation Tries its best Error often earlier Remember: JavaScript executes one statement at a time in order Track work Can leave it forever
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Variables
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Variable Values Save into a variable and the value changes Use a variable (like printing) and the value does NOT change
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Illustration
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JavaScript Function
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What is a function? Collection of statements that can be invoked as a unit Because sometimes we want to do more that a single assignment!
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Different Types of Functions
Who writes? JavaScript provides Someone else writes & you use You write
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Does function need information?
Alert does…tell it what to write Asking for a random number doesn’t Always need to use () Pass data if needed () if not
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Parameters Math.round: Number to round
Call a function with a different value every time MUST give it everything that it expects alert or console.log: string to print Math.round: Number to round
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Statement or part of an expression
Alert is a statement; doesn’t give you anything back If you ask for a random number, you expect to get something back
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Functions as Statements
Performs an action but doesn’t give you anything back Example: alert
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Alert String to print Function
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Writing a Function
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Format of a Function functionName(parm,parm);
Always needs () even if no parameter functionName(); For now: no parameter
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JavaScript Functions Summary
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alert console.log Takes an input value (string)
Does not return a value
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Getting a random number
Math.random() Does not need any inputs Returns a value between 0 and 1
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Other math functions Take an input value (number)
Math.round(num) Math.floor(num) Math.ceil(num) Take an input value (number) Return a value (number)
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Connecting JavaScript to HTML
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Where Do JavaScript Functions Go?
Like CSS, can be inline or a separate file Like CSS, an external file is considered better practice Like CSS, link to it from the head section
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A Separate JavaScript File
<script src="myscripts.js"></script> Myscript.js JavaScript option in komodo will work on it next
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FUNCTION: connecting to HTML
<head> <script src=“function.js”></script> </head> <body> <button type=“button” onclick=“doit();”> </body> HTML file name function name function doit () { alert(“Hi!”); } JAVASCRIPT (function.js)
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