Javascript

A couple of weeks back I posted how to pad a number with leading zeroes in Javascript as a lead-in to a post about how to format a date time in Javascript in database format. The original post used a while() loop to add zeroes on to the string but as pointed out to me by Greg Jorgensen it’s not very efficient so I present his solution here.

As far as I have been able to tell there isn’t a built-in way with Javascript to pad a number with leading zeroes to make it a fixed width like with e.g. sprintf in other programming langages. This post looks at a way to pad a number with zeroes with Javascript.

In some admin forms for own purposes I needed to have a "now" function to put the current date and time into the text field using Javascript. For various reasons I preferred to do this on the client side with Javascript than on the server side with PHP. The date and time format needed to be in a database YYYY-MM-DD HH:MM:SS format so it could be directly inserted into the database.

On Sunday I looked at how to pad a number with leading zeroes in Javascript and in this post look at a simpler function to pad a number to just two digits as if required for days and months, and hours, minutes and seconds.

This post looks at how to loop through an associate array with Javascript and display the key value pairs from the array. An associative array can contain string based keys instead of zero or one-based numeric keys in a regular array.

I saw a post on a bulletin board somewhere recently where the poster asked how to make the href work normally on a link like this <a href=”javascript:;” onclick=”dosomething()”> if Javascript is not enabled. It’s actually quite simple and I will look at how to do this in this post.

To make the browser go to e.g. otherpage.html if Javascript is not enabled, and instead execute the Javascript and don’t go to that page if Javascript is enabled, set the href to otherpage.html and return false from the Javascript function as shown in the code snippet below.

<a href="otherpage.html" onclick="return dosomething()">link</a>
 
 <script language="javascript">
 
 function dosomething() {
     ... code here ...
     return false;
 }
 
 </script>

The important thing to remember is the onclick needs to have “return” before the function call and the function must return false. If you still wanted the browser to go to otherpage.html after the function call you can simply leave out the return portions, or return true.

This also means you can conditionally allow the browser to go to otherpage.html by returning true or false depending on the condition. For example, you (wouldn’t really want to do this example but you) could prompt the user to see if they really do want to go to that link. If Javascript is disabled clicking it will simply take them there anyway.

<a href="otherpage.html" onclick="return dosomething(this)">link</a>
 
 <script language="javascript">
 
 function dosomething(a) {
 return window.confirm('Go to ' + a.href + '?');
 }
 
 </script

Another time I’ll look at how to manipulate the <a> tags in a page with conventional Javascript and also with jQuery. I do this on this site with conventional Javascript to track outbound links; without Javascript they are regular links but after the page has loaded they convert to trackable links.