CallExpression

CallExpression is a node in an abstract syntax tree (AST) used to represent a function or method invocation in JavaScript and related languages. It is a standard node type in ESTree, which underpins most JavaScript tooling such as Babel, ESLint, Esprima, and TypeScript’s AST representation.

Shape and fields: A CallExpression has a type field with the value "CallExpression", a callee field that holds an expression yielding the function to call, and an arguments field, an array of expressions to be evaluated and passed as parameters. Depending on the parser or language variant, there may be additional flags or node types to represent optional chaining.

Examples: The code f(1, 2) is represented as a CallExpression where callee is the Identifier "f" and arguments are [Literal 1, Literal 2]. The code obj.method(a) uses callee as a MemberExpression representing the property access "obj.method".

Evaluation: When evaluated, the callee is first evaluated to a function value, each argument expression is evaluated, and the function is invoked with those values. The this binding inside the function depends on how the call is performed (for example, obj.method() binds this to obj).

Variants and related forms: CallExpression is distinct from NewExpression, which constructs a new object, and from MemberExpression, which denotes property access on an object used as a callee. In modern tooling, optional chaining with a call may be represented by a separate OptionalCallExpression node or by a flag indicating optional behavior on the call.