Just recently I had to implement an HTML form that allows users to enter percentage values. Like every good programmer I added client-side validation to check that the input values are between 0 and 100.
My first reaction was to restrict the maxlength attribute of the input field to 3 characters only. Even though this is a good and recommended practise there was clearly something else wrong.
The parseInt() function parses a string and returns an integer. The signature is
parseInt(string, radix) with
- string (required) being the string to be parsed, and
- radix (optional) a number (from 2 to 36) that represents the numeral system to be used
- If the string begins with “0x”, the radix is 16 (hexadecimal)
- If the string begins with “0”, the radix is 8 (octal)
- If the string begins with any other value, the radix is 10 (decimal)
PS.: Only the first number in the string is returned!
PPS.: Leading and trailing spaces are allowed.
PPPS.: If the first character cannot be converted to a number, parseInt() returns NaN.
First impressions matter! Luke Wroblewski, an excellent speaker with original insights which I had the pleasure to hear at last year's UI-12 (User Interface 12) in Boston, states in his latest article that users coming to your site from a search engine will do one of three things:
- Look over the page and determine it is not relevant to their goal
- Look over the page and determine it might be relevant to their goals then quickly scan the page for the information they need
- Look over the page, quickly scan the page, find the information they need and then stay awhile.
All this happens within seconds. Therefore it is necessary to translate the first impressions (what am I looking at? functional role present?) into meaningful interactions, i.e. scanability, further (inter)action, which leaves us with the following
Guidelines for Visual Web Design
- Set initial expectations by communicating what kind of information it provides.
- Provide a way to quickly scan that information in order to locate something of value.
- Allow people to immerse themselves in the information they want and explore other relevant information when they choose to.