RSS

Validate numbers in JavaScript

21 Jun

Check your input with the following function:

function isNumber(n) {
return !isNaN(parseFloat(n)) && isFinite(n);
}

You can use another function:

function IsNumeric(input)
{
return (input - 0) == input && input.length > 0;
}

The (input – 0) expression forces JavaScript to do type coercion on your input value; it must first be interpreted as a number for the boolean compare. If that conversion to a number fails, the expression will result in NaN. Then this numeric result is compared to the original value you passed in. Since the left hand side is a number, type coercion is again used. They should always be the same (always true), but there’s a special rule that says NaN is never equal to NaN, and so a value that can’t be converted to a number will always return false. The check on the length is of course for the empty string special case. In summary, if you want to know if a value can be converted to a number, actually try to convert it to a number.

Note that it falls down on your 0x89f test, but that’s because in many environments that’s an okay way to define a number literal. If you want to catch that specific scenario you could add an additional check. Even better, if that’s your reason for not using isNaN() then just wrap your own function around isNaN() that can also do the additional check.

Here is another one:

function isNumeric(input) {
var number = /^\-{0,1}(?:[0-9]+){0,1}(?:\.[0-9]+){0,1}$/i;
var regex = RegExp(number);
return regex.test(input) && input.length>0;
}

Integer value can be verified by:

function isNumeric(value) {
var bool = isNaN(+value));
bool = bool || (value.indexOf('.') != -1);
bool = bool || (value.indexOf(",") != -1);
return !bool;
}
Advertisements
 
Leave a comment

Posted by on June 21, 2011 in JavaScript, Mixed

 

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

 
%d bloggers like this: