setInterval() callback to control the clock hands by rotating them based on the current time.
The following Vue concepts are discussed in this article:
- The HTML section fit inside the root
- The functions went into the
<style>section was moved into my Vue version unchanged
watchsections were not needed so they were removed
With those changes we can get pretty close to a working clock but not quite. The
querySelector() calls don’t have a place to go; without those, the rotation transforms aren’t going to work. To fix this I made just a couple of changes. First, I added three fields to the Vue Instance data object:
hourDegrees. These will hold the values in degrees for each clock hand.
Next, I changed the
setDate method to update those data fields. Note the usage of
this to reference the proper data fields within the Vue instance.
Then, I added a method
transformHandStyle that returns the transform style using degrees as its input.
And finally, I used Vue’s
:style binding to set the clock hands to the result of the
transformHandStyle method that is passed the corresponding data field.
Now let’s take a look at what the core of what the implementation looks like. I’ve annotated it to show how how it flows together.
- When the Vue instance is mounted, the
setDatemethod is called at intervals of 1 second (1000ms).
- Inside the
setDatefunction, the calculations for each hand is computed and set in the appropriate data field.
- Changes to the
hourDegreesdata fields activate Vue’s reactivity system to trigger calling the
transformHandStylemethod which sets the clock hand style.
transformHandStylemethod returns the css transform that rotates the clock hand.