Stage 1 Draft / November 10, 2023

Negated in and instanceof operators

1 Relational Operators

Note 1

The result of evaluating a relational operator is always of type Boolean, reflecting whether the relationship named by the operator holds between its two operands.

Syntax

RelationalExpression[In, Yield, Await] : ShiftExpression[?Yield, ?Await] RelationalExpression[?In, ?Yield, ?Await] < ShiftExpression[?Yield, ?Await] RelationalExpression[?In, ?Yield, ?Await] > ShiftExpression[?Yield, ?Await] RelationalExpression[?In, ?Yield, ?Await] <= ShiftExpression[?Yield, ?Await] RelationalExpression[?In, ?Yield, ?Await] >= ShiftExpression[?Yield, ?Await] RelationalExpression[?In, ?Yield, ?Await] instanceof ShiftExpression[?Yield, ?Await] RelationalExpression[?In, ?Yield, ?Await] !instanceof ShiftExpression[?Yield, ?Await] [+In] RelationalExpression[+In, ?Yield, ?Await] in ShiftExpression[?Yield, ?Await] RelationalExpression[?In, ?Yield, ?Await] !in ShiftExpression[?Yield, ?Await] [+In] PrivateIdentifier in ShiftExpression[?Yield, ?Await] Note 2

The [In] grammar parameter is needed to avoid confusing the in operator in a relational expression with the in operator in a for statement.

1.1 Runtime Semantics: Evaluation

RelationalExpression : RelationalExpression < ShiftExpression
  1. Let lref be ? Evaluation of RelationalExpression.
  2. Let lval be ? GetValue(lref).
  3. Let rref be ? Evaluation of ShiftExpression.
  4. Let rval be ? GetValue(rref).
  5. Let r be ? IsLessThan(lval, rval, true).
  6. If r is undefined, return false. Otherwise, return r.
 RelationalExpression : RelationalExpression > ShiftExpression
  1. Let lref be ? Evaluation of RelationalExpression.
  2. Let lval be ? GetValue(lref).
  3. Let rref be ? Evaluation of ShiftExpression.
  4. Let rval be ? GetValue(rref).
  5. Let r be ? IsLessThan(rval, lval, false).
  6. If r is undefined, return false. Otherwise, return r.
 RelationalExpression : RelationalExpression <= ShiftExpression
  1. Let lref be ? Evaluation of RelationalExpression.
  2. Let lval be ? GetValue(lref).
  3. Let rref be ? Evaluation of ShiftExpression.
  4. Let rval be ? GetValue(rref).
  5. Let r be ? IsLessThan(rval, lval, false).
  6. If r is either true or undefined, return false. Otherwise, return true.
 RelationalExpression : RelationalExpression >= ShiftExpression
  1. Let lref be ? Evaluation of RelationalExpression.
  2. Let lval be ? GetValue(lref).
  3. Let rref be ? Evaluation of ShiftExpression.
  4. Let rval be ? GetValue(rref).
  5. Let r be ? IsLessThan(lval, rval, true).
  6. If r is either true or undefined, return false. Otherwise, return true.
 RelationalExpression : RelationalExpression instanceof ShiftExpression
  1. Let lref be ? Evaluation of RelationalExpression.
  2. Let lval be ? GetValue(lref).
  3. Let rref be ? Evaluation of ShiftExpression.
  4. Let rval be ? GetValue(rref).
  5. Return ? InstanceofOperator(lval, rval).
 RelationalExpression : RelationalExpression !instanceof ShiftExpression
  1. Let lref be ? Evaluation of RelationalExpression.
  2. Let lval be ? GetValue(lref).
  3. Let rref be ? Evaluation of ShiftExpression.
  4. Let rval be ? GetValue(rref).
  5. Let r be ? InstanceofOperator(lval, rval).
  6. If r is true, return false. Otherwise, return true.
 RelationalExpression : RelationalExpression in ShiftExpression
  1. Let lref be ? Evaluation of RelationalExpression.
  2. Let lval be ? GetValue(lref).
  3. Let rref be ? Evaluation of ShiftExpression.
  4. Let rval be ? GetValue(rref).
  5. If rval is not an Object, throw a TypeError exception.
  6. Return ? HasProperty(rval, ? ToPropertyKey(lval)).
 RelationalExpression : RelationalExpression !in ShiftExpression
  1. Let lref be ? Evaluation of RelationalExpression.
  2. Let lval be ? GetValue(lref).
  3. Let rref be ? Evaluation of ShiftExpression.
  4. Let rval be ? GetValue(rref).
  5. If rval is not an Object, throw a TypeError exception.
  6. Let r be ? HasProperty(rval, ? ToPropertyKey(lval)).
  7. If r is true, return false. Otherwise, return true.
 RelationalExpression : PrivateIdentifier in ShiftExpression
  1. Let privateIdentifier be the StringValue of PrivateIdentifier.
  2. Let rref be ? Evaluation of ShiftExpression.
  3. Let rval be ? GetValue(rref).
  4. If rval is not an Object, throw a TypeError exception.
  5. Let privateEnv be the running execution context's PrivateEnvironment.
  6. Let privateName be ResolvePrivateIdentifier(privateEnv, privateIdentifier).
  7. If PrivateElementFind(rval, privateName) is not empty, return true.
  8. Return false.

A Copyright & Software License

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© 2023 Pablo Gorostiaga Belio

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