Month: September 2014

Preventing backspace from navigating your web page

I was running into problems where a user would have clicked outside of an input box and then type a backspace key and have the webpage navigate back one page. I tried a couple of solutions of my own, but they weren’t working.

I found this Stackoverflow solution which fixed the problem.


// Prevent the backspace key from navigating back.
$(document).unbind('keydown').bind('keydown', function (event) {
var doPrevent = false;
if (event.keyCode === 8) {
var d = event.srcElement || event.target;
if ((d.tagName.toUpperCase() === 'INPUT' &&
(
d.type.toUpperCase() === 'TEXT' ||
d.type.toUpperCase() === 'PASSWORD' ||
d.type.toUpperCase() === 'FILE' ||
d.type.toUpperCase() === 'EMAIL' ||
d.type.toUpperCase() === 'SEARCH' ||
d.type.toUpperCase() === 'DATE' )
) ||
d.tagName.toUpperCase() === 'TEXTAREA') {
doPrevent = d.readOnly || d.disabled;
}
else {
doPrevent = true;
}
}

if (doPrevent) {
event.preventDefault();
}
});

Knockout Auto-complete

I have been using knockout.js extensively in a recent project. I have enjoyed using it. The two-way data-binding has really simplified syncing the display and data, as well as posting data back to the server. I have found the documentation to be superb. Anything that I didn’t find in the documentation, I was able to learn with a quick google and usually found the result I needed on stackoverflow.com.

One feature that wasn’t explained well in the documentation was linking knockout to jQueryUI’s Auto-complete. I found several other blog posts from other people that had implemented it, but I think this post provided the best implementation. There were a couple of items that I tweaked to make it work closer to the way I wanted.

The first change was in the knockout custom binding. On the input text box, I had also defined a change event binding. The event binding was not getting called. There is a function named updateElementValueWithLabel in the definition that is called whenever an item was selected, changed or focused. I added this code to the bottom of the function:

if(typeof allBindings.event.change !== "undefined") {
allBindings.event.change();
}

This code enabled the change event binding to be called. It did create another problem. The above function was also being called when on option was moused over which triggered a focus event in the autocomplete plugin. I didn’t need the change event fired on just receiving focus, so this led to the second change I made.

In the jQueryUI section of the code, I changed the focus option to run just one line of code instead of calling the updateElementValueWithLabel function. That code was:
$(element).val(ui.item.label);
That line placed the option value in the html text box. When someone tabbed out or hit the enter key, the select/change functions would then be called.

I appreciate all the work the original author put in to develop this code. It saved me a tremendous amount of time in figuring out how to implement this and I only needed to make some minor tweaks to get it to work the way I needed it. Thanks Cameron.