Check if the date range is already parsed

[noxer]

I've encountered an error when attempting to use updateGraph. The visavail tries to match the Date objects it parsed in the first generate call with the regexes. This PR adds a type check to prevent this.

Caveat: I was unable to generate the minified version due to my enviroment here.

[tanganellilore]

Hi @noxer ,
can you replicate this error on a codesandbox.io ?

I'm not 100% sure that your workaround is correct because when we use the display_date_range we need to be sure that format of time is in the correct form, as same form generated by graph.

[noxer]

Without the fix I'm getting this exception when calling updateGraph:

Uncaught Error: Option of Display range Date/time format not recognized. Pick between 'YYYY-MM-DD' or 'YYYY-MM-DD HH:MM:SS'.
    at HTMLParagraphElement.drawGraph (visavail.js:458)
    at Selection.selection_each [as each] (d3.min.js:1176)
    at chart (visavail.js:278)
    at Selection.selection_call [as call] (d3.min.js:1140)
    at Function.chart.createGraph (visavail.js:1475)
    at Function.chart.updateGraph (visavail.js:1464)
    at updateMeasure (index.html:160)
    at HTMLInputElement.onchange (index.html:59)

The code still checks for the correct format of the timestamps, it just skips that check if the timestamp has already been converted into a Date object.

[tanganellilore]

Close this merge with new release of visavail 1.3.0.

Enjoy