Javascript - making this code efficient

Question

Its a relatively simple question however I wanted to see how other people would tackle the below issue:

A user can enter (x) quantity in to text box txtUserInput

so for example UserInput = 14

1 box can contain upto 4 items.

so based on the above txtUserInput, I want the program to calculate how many boxes are required, (in this case the answer would be 4 boxes, with 2 spaces remaining in the final box.

below is an example of the code in its basic form:

var itemsCount = txtUserInput;
var boxes = 0;

if (itemsCount <=4) {
boxes ++;
}

else if (itemsCount <=8 && >4) {
boxes += 2;
}

as you can see, I could repeat this over and over again to get the correct result but it would become very tedious and a lot longer than it requires...

So using JavaScript how can I put this into an array/loop and get boxes to give me my desired output?

thankyou for your help

@Crezzer7 Combine division and rounding up, and you have your answer. — JLRishe
– JLRishe, Commented May 15, 2015 at 16:24

Denys Séguret · Accepted Answer · 2015-05-15 16:22:51Z

5

Don't loop, do a division and then round up:

var boxes = Math.ceil(itemsCount / 4);

edited May 15, 2015 at 16:22

answered May 15, 2015 at 16:22

Denys Séguret

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4 Comments

Crezzer7 Over a year ago

what does that code do? i find javascript's logic very different to that of C# when it comes to thinks like this... thanks for your post

Felix Kling Over a year ago

@Crezzer7: What exactly is unclear? itemsCount / 4 is division. It divides the value of itemsCount by 4. You can learn more about division on Wikipedia: en.wikipedia.org/wiki/Division_(mathematics) . Math.ceil is a function (en.wikipedia.org/wiki/Function_(mathematics) , en.wikipedia.org/wiki/Subroutine ). A function accepts an input and returns an input. This function accepts a number, rounds it up and returns the result. You can learn more about rounding on Wikipedia: en.wikipedia.org/wiki/Floor_and_ceiling_functions

Cristik Over a year ago

For someone with C# experience as you say you have, you shoud know that Math.Ceiling(value) from C# is very similar to Math.ceil(value) from javascript.

Sterling Archer Over a year ago

the truncated method name really does throw you a curve ball though

Guffa · Accepted Answer · 2015-05-15 16:32:48Z

1

With your approach of checking how many boxes are needed, you would use a loop instead of having code for all possible number of boxes:

var boxes = 0;
while (itemsCount > 0) {
  boxes++;
  itemsCount -= 4;
}

However, you don't need a loop for this. You can just divide the number of items by four, and make sure that any fraction in the result causes another box to be used by rounding up:

var boxes = Math.ceil(itemsCount / 4);

For example dividing 14 by four gives the result 3.5, and rounding up gives you 4.

answered May 15, 2015 at 16:32

Guffa

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1 Comment

Crezzer7 Over a year ago

thanks for another alternative... this is what i was thinking

Matthew de Nobrega · Accepted Answer · 2015-05-15 16:33:27Z

1

You can use Math.ceil to round up after dividing the number of items by the size of the boxes (in this case 4);

var boxes = Math.ceil(txtUserInput/4);

Javascript's type coercion will handle an empty input (if txtUserInput is null) as zero automatically.

edited May 15, 2015 at 16:33

answered May 15, 2015 at 16:28

Matthew de Nobrega

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1 Comment

Crezzer7 Over a year ago

ok thanks, this may look like a dumb question to people who are used to Javascript, but i would do this very differently in C#, thanks for your answer

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