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Conditions and More Web Form Fields

Conditions and More Web Form Fields. Conditions. if (then) else Syntax. if. (. ). Boolean expression. {. instructions if expression is true (then). }. else. {. instructions if expression is false. }. Example. Check age. < 59. >=59 and <65. >65. Gotta Work!. Early Retirement?.

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Conditions and More Web Form Fields

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  1. Conditions and More Web Form Fields

  2. Conditions

  3. if (then) else Syntax if ( ) Boolean expression { instructions if expression is true (then) } else { instructions if expression is false }

  4. Example Check age < 59 >=59 and <65 >65 Gotta Work! Early Retirement? Retire!

  5. Example – Step 1 if ( age < 59 ) { alert(‘Gotta Work!’) }

  6. if ( age < 59 ) if ( age >= 59 && age < 65 ) Example – Step 2 { alert(‘Gotta Work!’) } else { (age >= 59) && (age < 65) { alert(‘Early Retirement?’) } }

  7. if ( age < 59 ) if ( (age >= 59) && (age < 65) ) Example – Step 2 (v2) { alert(‘Gotta Work!’) } else { alert(‘Early Retirement?’) }

  8. if ( age < 59 ) if ( (age >= 59) && (age < 65) ) Example – Step 3 { alert(‘Gotta Work!’) } else { alert(‘Early Retirement?’) } else { alert(‘Retire!’) }

  9. if ( age < 59 ) if ( (age >= 59) && (age < 65) ) Example – Step 3 (v2) { alert(‘Gotta Work!’) } else { alert(‘Early Retirement?’) } else { alert(‘Retire!’) }

  10. Relational Operators Equal to == > Greater than < Less than >= Greater than or equal to <= Less than or equal to != Not equal to

  11. Danger Will Robinson function check(p) { var a = p alert('initial a = ' + a) if (a = 5) { alert('if a = 5') } alert('final a = ' + a) } a == 5 JavaScript assignment statements execute and evaluate to true. check(10) initial a = 10 if a = 5 final a = 5

  12. Boolean Expression if ( (age >= 59) && (age < 65) ) Condition 1 Condition 2 Expressions and Conditions

  13. AND and OR AND && if (condition1 && condition2) Both conditions true  expression is true. Otherwise expression is false. OR || if (condition1 || condition2) Either condition true  expression is true.

  14. More Web Form Fields

  15. <input type="checkbox" name="student" checked="checked" /> Checkbox

  16. Checkbox document . form . field . checked document.getstuff.student.checked Boolean true or false

  17. Index = 0 Index = 1 <input type="radio" name="sex" id="male" value="M" /> <input type="radio" name="sex" Id="female" value="F" /> Radio Button Gender: Male <input type="radio" name="sex" id="male" value="M" /> Female <input type="radio" name="sex" id="female" value="F" />

  18. var message var indx message = ‘by Index using Checked property\n‘ for (indx = 0; indx < document.getstuff.sex.length; indx++) { message = message + 'Indx=' + indx + ' checked=' + document.getstuff.sex[indx].checked + '\n‘ } alert(message)

  19. message = ‘by Index using Value property\n‘ for (indx = 0; indx < document.getstuff.sex.length; indx++) { message = message + 'Indx=' + indx + ' value=' + document.getstuff.sex[indx].value + '\n‘ } alert(message)

  20. message = ‘by d.f.id.checked\n‘ message = message + 'document.getstuff.male.checked=' + document.getstuff.male.checked + '\n‘ message = message + 'document.getstuff.female.checked=' + document.getstuff.female.checked + '\n‘ alert(message)

  21. <select name="major"> <option value="mis">Management Information Systems</option> <option value="cis">Computer Information Systems</option> <option value="isp">Information Security and Privacy</option> </select> Select and Option

  22. Select and Option document . form . field . value document.getstuff.major.value <select name="major"> <option value="mis">Management Information Systems</option> <option value="cis">Computer Information Systems</option> <option value="isp">Information Security and Privacy</option> </select>

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