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# This CGI script uses JavaScript to validate a form before submission.
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title "Using JavaScript to validate a form before submission"
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if (num.value % 2 == 0) {
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alert("Please enter an odd number!")
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puts "Sorry - your browser doesn't understand JavaScript."
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proc row {msg {event {}}} {
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text num$rownum= size=4 $event
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if {0 == [catch {import num3}]} {
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set count [scan $num3 %d num]
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if {($count != 1) || ($num % 2 == 0)} {
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p "Hey, you didn't enter an odd number!"
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p "Thanks for entering odd numbers!"
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puts "Please enter$more odd numbers - thanks!"
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cgi_form validate "onSubmit=return odd(this.num2)" {
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row "This number will be validated when it is entered." onChange=odd(this.form.num1)
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row "This number will be validated when the form is submitted."
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row "This number will be validated after the form is submitted."
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h5 "Note: JavaScript validation should always be accompanied
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by validation in the backend (CGI script) since browsers
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cannot be relied upon to have JavaScript enabled (or supported
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in the first place). Sigh."