Selecting identifiers

Perhaps the most basic - and common - expression is the Identifier expression: it is what we use to refer to the callee x in the function call x(), or the property a in the object literal { a: 1 }, or the parameter a in the declaration function x(a) {}.

(id) selects identifiers that appear on their own or in other expressions. The following query will match x in the expression x + y, the declaration function a(x) {}, or the call x():

(id x)

Anywhere an Identifier is allowed in JavaScript, the (id) selector is also allowed in SYNG queries.

Shorthand form

Because identifiers are very common, SYNG provides a shorthand for this selector in the form of the identifier atom:

x

The above expands into the selector we saw earlier: (id x). This form is convenient when we're selecting identifiers as part of other expressions:

(call x) ; or
(call (id x))

The above two queries are equivalent. While we haven't encountered the (call) selector yet, it is enough to know that the shorthand exists for now.