Chapter 10: JavaScript Functions CIS 275—Web Application Development for Business I.
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Chapter 10: JavaScript Functions CIS 275—Web Application Development for Business I
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Transcript of Chapter 10: JavaScript Functions CIS 275—Web Application Development for Business I.
Chapter 10: JavaScript Functions
CIS 275—Web Application Development for Business I
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Program Modules in JavaScript
Software development is best achieved in smaller pieces called _________, applying the principle of “divide and conquer”.
A module in JavaScript is called a _________. A pre-defined function that belongs to a class is
called a method (like Math.pow or Math.round). A function you write is called a ____________-
defined function. A function is invoked by a function call. A function call may include arguments. A called function may _______ data to the caller.
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Programmer-Defined Functions
All variables declared in a function are _______. A function declaration may include
parameters, which are also local variables. Functions enable the principle of software
reuse and help to avoid code repetition. Format of a function definition
function function-name ( parameter-list ) {
declarations and statements}
The ___ is the function call operator. The first line is the function declaration and the
content within the {}’s is the function ______.
()
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Fig. 10.2<html xmlns = "http://www.w3.org/1999/xhtml"> <head> <title>A Programmer-Defined Function</title> <script type = "text/javascript"> document.writeln( "<h1>Square numbers from 1 to 10</h1>" ); for ( var x = 1; x <= 10; ++x ) document.writeln( "The square of " + x +
" is " + square( x ) + "<br />" ); function square( y ) // do NOT use var here { return y * y; } </script> </head> <body></body></html>
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Example of a Function Call<html><head><script type="text/javascript">
function myFunction(){alert("HELLO")
}</script></head><body><form><input type = "button" onclick = "myFunction()" value = "Call function" ></form><p>By pressing the button, a function will be called. The
function will alert a message.</p></body></html>
Function Call w/ Arguments and Return<?xml version = "1.0"?><!DOCTYPE htmlPUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"><html><head><script type="text/javascript">
function total(numberA, numberB){return numberA + numberB
}</script></head>
<body><script type="text/javascript">
document.write( total(2,3) )</script></body></html>
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10.8 Scope Rules The scope of an identifier for a variable or
function is the part of the program in which the identifier can be referenced.
Variables declared in the ______ element are global variables and have global scope.
Variables declared inside a function have ______ scope and can be used only in that function.
Function parameters also have local scope. A variable with local scope will ______ a
variable with the same name that has global scope.
