I’m confused by Observable’s use of the word "operator" in their documentation, and wondering whether they have misused it, or I’m simply not understanding.
Observable has a special
viewof
operator which lets you define interactive values. A view is a cell with two faces: its user interface, and its programmatic value.
viewof text = html.html`<input value="edit me">
The
viewof
operator namedtext
renders a text field. The value of that field can be accessed elsewhere by callingtext
.
https://observablehq.com/documentation/cells/observable-javascript
In this context, the bit to the right of = is JavaScript, and the bit to the left is special Observable syntax. text =
is what they call a variable assignment (similar-ish to a JS variable declaration).
Adding viewof
beforehand changes the semantics of the declaration, similar (to me) to how one might add public
or static
before declarations in other contexts.
(Observable has another such "operator", mutable
).
Is it reasonable to describe this as an "operator"? And if not, what would a better term be?
2
Answers
The term operator doesn’t have a very precise definition that holds across all languages, but it usually refers to something that’s used in expressions. For example, the ECMAScript spec (which defines what we think of as JavaScript) currently says:
That’s not a definition, and so far as I can tell it’s not a complete list (it seems to be missing newer operators; for example, none of its categories seems to cover nullish coalescing and optional chaining, each of which is described as an "operator" in the list of changes made in ECMAScript 2020), but I think it supports the intuition that operators appear in expressions.
From your explanation, it doesn’t sound like
viewof
meets that criterion, so I agree with your sense that that’s not the right term. I think I would say that it belongs to the broader category of "keywords" or "reserved words".While there is no strict definition for the term operator, it usually refers to a syntactical construct that lets you combine an expression from other expressions. It may also involve other constituents though, like when you say that the
.
operations combines an expression and a name into a property access expression.However,
var
/let
/const
are typically not considered operators since they don’t build an expression, but rather a declaration statement. Theviewof
in your example appears to fall into the same category. It’s just a keyword.