Copyright © Terry Felke-Morris WEB DEVELOPMENT & DESIGN FOUNDATIONS WITH HTML5 7 TH EDITION Chapter 14 Key Concepts 1 Copyright © Terry Felke-Morris

ARITHMETIC OPERATORS OperatorDescriptionExampleValue of Quantity =assignquantity = additionquantity = subtractionquantity = *multiplicationquantity = 10 * 220 /divisionquantity = 10 / 25 2

COMPARISON OPERATORS OperatorDescriptionExampleSample values of quantity that would result in true = =Double equals sign (equivalent) “is exactly equal to” quantity = = 1010 >Greater thanquantity > 1011, 12 (but not 10) > =Greater than or equal to quantity > = 1010, 11, 12 <Less thanquantity < 108, 9 (but not 10) < =Less than or equal to quantity < = 108, 9, 10 ! =Not equal toquantity ! = 108, 9, 11 (but not 10) 3

Copyright © Terry Felke-Morris DECISION MAKING if (condition) { … commands to execute if condition is true } else { … commands to execute if condition is false } 4

Copyright © Terry Felke-Morris HANDS-ON PRACTICE 14.6  Page 576  chapter14/quantityif.html 5

Copyright © Terry Felke-Morris FUNCTION  A function is a block of one or more JavaScript statements with a specific purpose, which can be run when needed. function function_name() {... JavaScript statements … } 6

Copyright © Terry Felke-Morris USING FUNCTIONS function showAlert() { alert("Please click OK to continue."); } 7 Calling the Function showAlert(); Defining the Function

Copyright © Terry Felke-Morris HANDS-ON PRACTICE 14.7  Page 579  chapter14/quantityif2.html 8

Copyright © Terry Felke-Morris FORM VALIDATION  It is common to use JavaScript to validate form information before submitting it to the web server.  Is the name entered?  Is the address of correct format?  Is the phone number in the correct format?  See Hands-on Practice

Copyright © Terry Felke-Morris VALIDATING FORM FIELDS  Use the "" or null to check to determine if a form field has information if (document.forms[0].userName.value == "" ) { alert("Name field cannot be empty."); return false; } // end if 10

Copyright © Terry Felke-Morris HANDS-ON PRACTICE 14.8  Page 582  chapter14/formvalidation.html 11

Copyright © Terry Felke-Morris JAVASCRIPT & ACCESSIBILITY  Don’t expect JavaScript to always function for every visitor  Some may have JavaScript disabled  Some may be physically unable to click a mouse  Provide a way for your site to be used if JavaScript is not functioning  Plain text links  contact info 12