What is the preferred way of working with dates and JavaScript? - faunadb

Question

When working with a Faunadb record that contains a date value, I struggled with using that date in JavaScript. Eventually I got it working like so:
project.shipDate = new Date(await client.query(q.Format('%t', project.shipDate)));
This seems fine, but I also noticed I could do this:
let test = JSON.parse(JSON.stringify(project.created));
console.log(test);
datetest = new Date(test["#date"]);
Which seems wonky (grin), but may be quicker as it's not using the Fauna client library. Which should I prefer?

Answer 1

The JS driver has several helper classes that let you cast the javascript Time and Date objects to their FQL counterparts.
Here is an example.
From Fauna to JS
You can create a new document that contains a date value.
const project = await client.query(
q.Create(
q.Collection("projects"),
{ data: { shipDate: q.ToDate(q.Now()) } }
)
)
You can retrieve the date value and use as a javascript Date object by using the value property
const shipDate = new Date(project.data.shipDate.value)
From JS to Fauna
The date value can be modified however you want, and you can pass it back to FQL using the values.FaunaDate class.
const { values } = require('faunadb')
/* ... */
let nextDay = new Date(shipDate.getTime() + 86400000)
const faunaDate = new values.FaunaDate(nextDay)
Full Example
const project = await client.query(
q.Create(
q.Collection("projects"),
{ data: { shipDate: q.ToDate(q.Now()) } }
)
)
console.log(project)
const shipDate = new Date(project.data.shipDate.value)
console.log(shipDate)
let nextDay = new Date(shipDate.getTime() + 86400000)
console.log(nextDay)
const projectRef = project.ref
const projectUpdate = await client.query(
q.Update(
projectRef,
{ data: { shipDate: new values.FaunaDate(nextDay) } }
)
)
console.log(projectUpdate)
{
ref: Ref(Collection("projects"), "307924674409398337"),
ts: 1629918703380000,
data: { shipDate: Date("2021-08-25") }
}
2021-08-25T00:00:00.000Z
2021-08-26T00:00:00.000Z
{
ref: Ref(Collection("projects"), "307924674409398337"),
ts: 1629918703470000,
data: { shipDate: Date("2021-08-26") }
}