Variable Scope - PowerPoint Presentation

Slide1

Variable Scope

Variable, variable, who’s got the variable?

© Copyright

2016,

Fred McClurg All Rights ReservedSlide2

Variable ScopeScope Defined:Variable scope has to do with where variables are “visible” in a program.Local Scope:Scope that is local to function and does not have a value outside the function.Global Scope:Scope that is visible inside and outside the function2Slide3

Global Variable ScopeVariables defined outside of the function have global scope.function clobber() { star = "John Wayne"; // note: no var keyword // displays "John Wayne" console.log( "Inside clobber(): " + star );}var star = "Danny Kaye"; // global variable// displays "Danny Kaye"console.log( "Before clobber(): " + star );

clobber(); // function call

// displays "John Wayne"console.log( "After clobber(): " + star );3

globalScope.htmlSlide4

Parameter Variable ScopeVariables passed to the function as arguments have local scope.function clobber( star ) { // local variable parameter // displays "Danny Kaye" console.log( "Inside clobber() before: " + star ); star = "John Wayne"; // displays "John Wayne" console.log( "In clobber() after: " + star );}var star = "Danny Kaye"; // global variable// displays "Danny Kaye"console.log( "Before clobber() call: " + star );

clobber( star ); // variable argument "Passed by Value"

// displays "Danny Kaye"console.log( "After clobber() call: " + star );4

paramScope.htmlSlide5

Local Variable ScopeVariables defined inside of the function have local scope.function clobber() { var star = "John Wayne"; // local variable // displays "John Wayne" console.log( "Inside clobber(): " + star );}var star = "Danny Kaye"; // global variable// displays "Danny Kaye"console.log( "Before clobber(): " + star );

clobber(); // function call

// displays "Danny Kaye"console.log( "After clobber(): " + star );5

localScope.html