Operator reference

Declarative expressions ( $expression ) admit a closed set of operators, enforced by the Jx schema. This page enumerates that set straight from packages/schema/schema.json . The expression model itself is documented in the Framework concepts section; named-formula composition is cataloged in the formula catalog .

Unary operators

Applied to a single target operand.

! · -

Binary operators

Applied to a target and a value operand. Arithmetic, comparison, logical, and nullish-coalescing forms — the blessed subset of JavaScript's operator set (spec §19.4).

+ · - · * · / · % · === · !== · < · <= · > · >= · && · || · ??

Assignment operators

Statement-position only: assign (or read-modify-write) a state path. Not valid inside pure expressions.

= · += · -= · *= · /=

Conditional, switch, and call

?: selects between value and else on a target condition; switch matches a target against cases ; call invokes a named formula (spec §19.4c) with args .

?: · switch · call

Pure standard-library methods

Genuine pure String / Array / Number prototype methods, usable inside pure expressions (spec §19.4d). The change-by-copy family ( toSorted , toReversed , toSpliced , with ) replaces their mutating counterparts.

includes · indexOf · lastIndexOf · join · slice · concat · at · flat · toSorted · toReversed · toSpliced · with · toUpperCase · toLowerCase · trim · trimStart · trimEnd · split · startsWith · endsWith · padStart · padEnd · replaceAll · repeat · charAt · normalize · toLocaleUpperCase · toLocaleLowerCase · toFixed · toPrecision · toLocaleString

Mutation methods

Statement-position array mutations. pop / shift take no argument; push / unshift take one; splice takes start , deleteCount , and items .

pop · shift · push · unshift · splice

Iteration methods

map / filter evaluate their value expression per item with $map/item and $map/index in scope; reduce additionally exposes $reduce/acc and takes an initial value.

reduce · map · filter