Stage -1 Draft / February 27, 2025

ECMAScript Try Operator

1 Assignment Operators

Syntax

AssignmentExpression[In, Yield, Await] : TryExpression[?In, ?Yield, ?Await] TryExpression[In, Yield, Await] : try [no LineTerminator here] [lookahead ≠ {] AssignmentExpression[?In, ?Yield, ?Await]

1.1 Runtime Semantics: Evaluation

TryExpression : try AssignmentExpression
  1. Let A be Completion(Evaluation of Expression).
  2. If A is an abrupt completion, return ? TryExpressionResult(A).
  3. Let B be Completion(GetValue(A)).
  4. Return ? TryExpressionResult(B).
 Note

GetValue must be called even though its value is not used because it may have observable side-effects.

1.2 TryExpressionResult ( result )

The abstract operation TryExpressionResult takes argument result (a Completion Record) and returns either a normal completion containing a Result or an abrupt completion. It performs the following steps when called:

  1. If result is a normal completion, return Result.ok(result.[[VALUE]]).
  2. If result is a throw completion, return Result.error(result.[[VALUE]]).
  3. Return ? result.

1.3 Result.ok ( value )

The abstract operation Result.ok takes argument value (an ECMAScript language value) and returns a Result. It is the abstract equivelant of calling Result.ok(value)

1.4 Result.error ( value )

The abstract operation Result.error takes argument value (an ECMAScript language value) and returns a Result. It is the abstract equivelant of calling Result.error(value)

2 Well-Known Intrinsic Objects

Table 1: Well-Known Intrinsic Objects
Intrinsic Name Global Name ECMAScript Language Association
%Result% Result The Result constructor (3)

3 The Result Constructor

The Result constructor:

A Copyright & Software License

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© 2025 Arthur Fiorette, Arlen Beiler

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