Tag Archives: application

AngularJS To do App – Part IV

Following from the previous entry, there was just one feature remaining for the rudimentary functionalities of our app:

  • Check of an item

I added an input checkbox to the ngRepeat construct. And after some fumbling around and going through some forums + angularjs developer documentation, I managed to apply a simple class styling to the item in the list when the checkbox is checked.

// Class applied when model ticked is true
<input type="checkbox" name="tickbox" ng-model="ticked" />
<span ng-class="{'checked': ticked}"> {{ item }} </span>

// CSS style that's applied
.checked {
text-decoration:line-through;
color: gainsboro;
}

This accomplishes a somewhat crude implementation of a To Do list item being checked off. However, the styling seems to fall through to the next item when a checked item is deleted. Also a checked item should preferably be locked from being edited.

So that still needs to be worked on and possibly some extra refactoring of the code in terms of button states as extra conditions required to prevent the fall through will only add to the growing list of conditions on some of the buttons already:

<button type="submit" ng-show="updateShow" ng-click="update($index, editedItem); updateShow= false; showEditInput = false; editShow = true;">Update</button>

Apart from that some aesthetic tweaks to the design and form is warranted. So stay tuned and check out the latest:

App – To Do | Commit

JavaScript binary to decimal application (Part Three): The Flux Capa… Convertor

Ok been on a hiatus due to work/college and most importantly my first born. So after a much waited delay, here’s the final piece – the actual conversion from Binary to Decimal.

This is the logic, which I took adapted from my Java lectures.

var convertToDecimal = function(binVal){
  var result = 0;
  var n = binVal.length - 1;
  for (i = 0; i < binVal.length; i++){
    var digit = binVal.charAt(i);
    result = result + (digit * Math.pow(2, n));
    n--;
  }
  return result;
}

This takes over from the last check, where we verified if an input was binary, and traverses the length of that input from left to right. Simultaneously var n is set to the positional power of the digit iterated over and added to the digit. The end result of all such additions is the decimal value.

Niggles encountered

I initially set the for loop check as n + 1; I erroneously assumed that since n was length minus one that would make up for the discrepancy, however each iteration would affect the value of n with the decrement (n–) and then the check would add 1 to it. I haven’t checked the full ramification of such a value but it did throw off conversion.

Another snag was that I was trying to set the output field’s value inside a conditional branch i.e.

if (value does not contain 1 or 0){  
  document.getElementById("output").value = input;
} else {
  /* code to execute if input is binary */
}

This was before, when I was doing a test to see output of invalid characters; input is the parameter passed to the function which contains the above conditional. That didn’t actually set the output as I’d expected. It somewhat makes sense when the function call is made – it is set to pass a value back, which expects a returned value.

document.getElementById("output").value = checkInput(binInput);

The line above can be taken to mean it would set it directly but wasn’t doing anything.

Closing Thoughts

So that pretty much wraps up the project in terms of the functionality and what was set out initially :

  • Creating a HTML/CSS/Javascript implementation of a problem we had to solve in a Java class – given a binary value, convert it to its decimal counterpart.
    • logic for the binary to decimal conversion.
    • restricting the entry value to 1’s and 0’s, probably using regular expression.

Further enhancements might be conducted to improve the user interface. One thing that came up during the exercise is that CodePen isn’t ideal for showing the various stages of the project. So each blog entry detailing the steps I’d taken will all point to the end result and not what it was like at that moment in time. Suppose that’s another issue to contend with if items are being created on CodePen. For the moment here is the completed, albeit unpolished, piece:

See the Pen
Binary to Decimal Conversion
by Donal D’silva (@donyd)
on CodePen.

JavaScript binary to decimal application (Part Two): Regular Expressions

Continuing on from the previous post, where I set up a pen on codepen.io to create a simple application that would take a binary number and covert to decimal. I’d laid out front end and the two tasks I had left were:

  • logic for the binary to decimal conversion.
  • restricting the entry value to 1’s and 0’s, probably using regular expression.

Filtering binary values using Regex

The one currently on my to do list is limit only binary values being entered into the input field. First hurdle was being able to compare the value input. Regex was my go to choice and was simple enough:

/[10]/g  -- pretty much translates to a range of digits from 1 to 0

However, there were a range of issues:

  • I assumed that even though the expression would find all instances of the pattern, it wasn’t working properly and I would have to create code to iterate through each character in the input [turned out I was using the wrong regex object methods i.e. match instead of test]
  • After finding the right method call ‘regex.test()’ the condition was picking some input which wasn’t binary.

My condition was

if (value contains 1 or 0) {
     /* code to execute if input is binary */
} else {
    /* code to execute if input isn't binary */
}

Any values which contained either a ‘1’ or ‘0’ would be accurately considered as binary figures. However, the issue was when a non valid input contained either of the valid elements ‘1’ or ‘0’ e.g. 10A, that would be considered binary as well.

I’d searched for numerous forums tips on pattern matching what was needed and excluding others i.e. show me only cases where it’s 1’s and 0’s and excluded everything else. Pretty sure there are ways but none that I could find.

Solution

The solution was very simple however, by seeking a pattern that considered everything except 1’s and 0’s and then using that as the filter to discount all non valid binary  input meant that the remaining items would surely be binary values.

if (value does not contain 1 or 0){  
  /* code to execute if not binary */
} else {
  /* code to execute if input is binary */
}

See the Pen xELLJP by Donal D’silva (@donyd) on CodePen.

Closing thoughts

The task was deceptively simple, even though it proved somewhat daunting in the beginning. Further excursions into Regex is warranted, just to get beyond the basic pattern matching that can be done. So with that we’re one step closer to the end goal.