In js, we need to check whether the variable is a number. We can directly use the isNaN function. The isNaN function judges the opposite. If you input a number, it returns false, not the data, you can clear this point.
IsNaN Function
IsNaN (expression: Object): Boolean
Common verification numbers
The Code is as follows: |
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Document. write (isNaN (123); // false Document. write (isNaN (-1.23); // false Document. write (isNaN (5-2); // false Document. write (isNaN (0); // false Document. write (isNaN ("Hello"); // true Document. write (isNaN ("2005/12/12"); // true Document. write (isNaN ("6/2"); // true Document. write (isNaN ("3"); // false |
Application Examples
The Code is as follows: |
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If (isNaN (document. login. imgcode. value )){ Alert ('verification code must be a number! ') Document. login. imgcode. focus (); Return false; }
If (! IsNum (document. getElementById ("prjSum"). value )){ Alert ("cost can only be a number "); Document. getElementById ("prjSum"). focus (); Return false;
} |