Syntax

Block :

{ StatementList_opt }

StatementList :

Statement
StatementList Statement

Semantics

The production Block : { } is evaluated as follows:

1. Return "normal completion".

The production Block : { StatementList } is evaluated as follows:

1. Evaluate StatementList.
2. Return Result(1).

The production StatementList : Statement is evaluated as follows:

1. Evaluate Statement .
2. Return Result(1).

The production StatementList : StatementList Statement is evaluated as follows:

1. Evaluate StatementList.
2. If Result(1) is an abrupt completion, return Result(1).
3. Evaluate Statement.
4. If Result(3) is a value completion, return Result(3).
5. If Result(1) is not a value completion, return Result(3).
6. Let V be the value carried by Result(1).
7. If Result(3) is "abrupt completion because of break ", return "abrupt completion after value V because of break ".
8. If Result(3) is "abrupt completion because of continue ", return "abrupt completion after value V because of continue ".
9. Return "normal completion after value V".

Syntax

VariableStatement :

var VariableDeclarationList ;

VariableDeclarationList :

VariableDeclaration
VariableDeclarationList , VariableDeclaration

VariableDeclaration :

Identifier Initializer_opt

Initializer :

= AssignmentExpression

Description

If the variable statement occurs inside a FunctionDeclaration , the variables are defined with function-local scope in that function, as described in section 10.1.3. Otherwise, they are defined with global scope (that is, they are created as members of the global object, as described in section 10.1.3) using property attributes { DontDelete }.. Variables are created when the execution scope is entered. A Block does not define a new execution scope. Only Program and FunctionDeclaration produce a new scope. Variables are initialised to the undefined value when created. A variable with an Initializer is assigned the value of its AssignmentExpression when the VariableStatement is executed, not when the variable is created.

Semantics

The production VariableStatement : var VariableDeclarationList ; is evaluated as follows:

1. Evaluate VariableDeclarationList.
2. Return "normal completion".

The production VariableDeclarationList : VariableDeclaration is evaluated as follows:

1. Evaluate VariableDeclaration.

The production VariableDeclarationList : VariableDeclarationList , VariableDeclaration is evaluated as follows:

1. Evaluate VariableDeclarationList.
2. Evaluate VariableDeclaration.

The production VariableDeclaration : Identifier is evaluated as follows:

1. Return a string value containing the same sequence of characters as in the Identifier .

The production VariableDeclaration : Identifier Initializer is evaluated as follows:

1. Evaluate Identifier as described in section 11.1.2.
2. Evaluate Initializer.
3. Call GetValue(Result(2)).
4. Call PutValue(Result(1), Result(3)).
5. Return a string value containing the same sequence of characters as in the Identifier .

The production Initializer : = AssignmentExpression is evaluated as follows:

1. Evaluate AssignmentExpression.
2. Return Result(1).

Syntax

EmptyStatement :

;

Semantics

The production EmptyStatement : ; is evaluated as follows:

1. Return "normal completion".

Syntax

ExpressionStatement :

[lookahead ∉ {{, function}] Expression ;

Semantics

The production ExpressionStatement : Expression ; is evaluated as follows:

1. Evaluate Expression .
2. Call GetValue(Result(1)).
3. Return "normal completion after value V", where the value V is Result(2).

Syntax

IfStatement :

if ( Expression ) Statement else Statement
if ( Expression ) Statement

Each else for which the choice of associated if is ambiguous shall be associated with the nearest possible if that would otherwise have no corresponding else .

Semantics

The production IfStatement : if ( Expression ) Statement else Statement is evaluated as follows:

1. Evaluate Expression .
2. Call GetValue(Result(1)).
3. Call ToBoolean(Result(2)).
4. If Result(3) is false , go to step 7.
5. Evaluate the first Statement .
6. Return Result(5).
7. Evaluate the second Statement .
8. Return Result(7).

The production IfStatement : if ( Expression ) Statement is evaluated as follows:

1. Evaluate Expression .
2. Call GetValue(Result(1)).
3. Call ToBoolean(Result(2)).
4. If Result(3) is false , return "normal completion".
5. Evaluate Statement .
6. Return Result(5).

An iteration statement consists of a header (which consists of a keyword and a parenthesized control construct) and a body (which consists of a Statement ).

Syntax

IterationStatement :

while ( Expression ) Statement
for ( Expression_opt ; Expression_opt ; Expression_opt ) Statement
for ( var VariableDeclarationList ; Expression_opt ; Expression_opt ) Statement
for ( LeftHandSideExpression in Expression ) Statement
for ( var Identifier Initializer_opt in Expression ) Statement

Syntax

ContinueStatement :

continue [no LineTerminator here] Identifier_opt ;

Semantics

An ECMAScript program is considered syntactically incorrect if it contains a continue statement that is not within a while or for statement. The continue statement is evaluated as:

1. Return "abrupt completion because of continue ".

Syntax

BreakStatement :

break [no LineTerminator here] Identifier_opt ;

Semantics

An ECMAScript program is considered syntactically incorrect if it contains a break statement that is not within a while or for statement. The break statement is evaluated as:

1. Return "abrupt completion because of break ".

Syntax

ReturnStatement :

return [no LineTerminator here] Expression_opt ;

Semantics

An ECMAScript program is considered syntactically incorrect if it contains a return statement that is not within the Block of a FunctionDeclaration . It causes a function to cease execution and return a value to the caller. If Expression is omitted, the return value is the undefined value. Otherwise, the return value is the value of Expression .

The production ReturnStatement :: return [no LineTerminator here] Expressionopt ; is evaluated as:

1. If the Expression is not present, return "abrupt completion because of return undefined ".
2. Evaluate Expression .
3. Call GetValue(Result(2)).
4. Return "abrupt completion because of return V ", where the value V is Result(3).

Syntax

WithStatement :

with ( Expression ) Statement

Description

The with statement adds a computed object to the front of the scope chain of the current execution context, then executes a statement with this augmented scope chain, then restores the scope chain.

Semantics

The production WithStatement : with ( Expression ) Statement is evaluated as follows:

1. Evaluate Expression .
2. Call GetValue(Result(1)).
3. Call ToObject(Result(2)).
4. Add Result(3) to the front of the scope chain.
5. Evaluate Statement using the augmented scope chain from step 4.
6. Remove Result(3) from the front of the scope chain.
7. Return Result(5).

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