August 1999
Intermediate to advanced
1488 pages
72h 53m
English
Content preview from Pure JavaScript
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Global.isNaN()
JavaScript 1.1+, JScript 1.0+ Nav3+, NES2+, IE 3+, Opera3+ Syntax
isNaN(variable)
Description
The isNaN() function is used to determine whether variable is a valid number.
Example
In Listing 6.138, you see how the isNaN() function can be used to check user input.
Listing 6.138 Example of isNaN() Function
<html> <body> <script lanuguage="JavaScript"> <!–– Hide function checkNum(){ var n = document.form1.text1.value; if(isNaN(n) == true){ alert("Your entry is not a number"); } } // End Hide –– > </script> <form name="form1"> Enter a number or character into the text box and then click the check value button to verify if the input is a number. <br><br> <input type="text" name="text1" size=3> <br><br> <input type="button" ... |
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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