ECMAScript® 2024 Language Specification

Draft ECMA-262 / December 6, 2023

14.11 The with Statement

Note 1

Use of the Legacy with statement is discouraged in new ECMAScript code. Consider alternatives that are permitted in both strict mode code and non-strict code, such as destructuring assignment.

Syntax

WithStatement[Yield, Await, Return] : with ( Expression[+In, ?Yield, ?Await] ) Statement[?Yield, ?Await, ?Return] Note 2

The with statement adds an Object Environment Record for a computed object to the lexical environment of the running execution context. It then executes a statement using this augmented lexical environment. Finally, it restores the original lexical environment.

14.11.1 Static Semantics: Early Errors

WithStatement : with ( Expression ) Statement Note

It is only necessary to apply the second rule if the extension specified in B.3.1 is implemented.

14.11.2 Runtime Semantics: Evaluation

WithStatement : with ( Expression ) Statement
  1. Let val be ? Evaluation of Expression.
  2. Let obj be ? ToObject(? GetValue(val)).
  3. Let oldEnv be the running execution context's LexicalEnvironment.
  4. Let newEnv be NewObjectEnvironment(obj, true, oldEnv).
  5. Set the running execution context's LexicalEnvironment to newEnv.
  6. Let C be Completion(Evaluation of Statement).
  7. Set the running execution context's LexicalEnvironment to oldEnv.
  8. Return ? UpdateEmpty(C, undefined).
 Note

No matter how control leaves the embedded Statement, whether normally or by some form of abrupt completion or exception, the LexicalEnvironment is always restored to its former state.