Пока что мы не говорим об объектах
В этой главе мы не касаемся объектов. Сначала мы разберём преобразование примитивных значений. Мы разберём преобразование объектов позже, в главе Преобразование объектов в примитивы.
12.8.3 The Addition Operator ( + )
NOTE
The addition operator either performs string concatenation or numeric addition.
12.8.3.1 Runtime Semantics: Evaluation
AdditiveExpression:AdditiveExpression+MultiplicativeExpression
Let lref be the result of evaluating AdditiveExpression.
Let lval be ? GetValue(lref).
Let rref be the result of evaluating MultiplicativeExpression.
Let rval be ? GetValue(rref).
Let lprim be ? ToPrimitive(lval).
Let rprim be ? ToPrimitive(rval).
If Type(lprim) is String or Type(rprim) is String, then
Let lstr be ? ToString(lprim).
Let rstr be ? ToString(rprim).
Return the string-concatenation of lstr and rstr.
Let lnum be ? ToNumber(lprim).
Let rnum be ? ToNumber(rprim).
Return the result of applying the addition operation to lnum and rnum. See the Note below 12.8.5.
NOTE 1
No hint is provided in the calls to ToPrimitive in steps 5 and 6. All standard objects except Date objects handle the absence of a hint as if the hint Number were given; Date objects handle the absence of a hint as if the hint String were given. Exotic objects may handle the absence of a hint in some other manner.
NOTE 2
Step 7 differs from step 3 of the Abstract Relational Comparison algorithm, by using the logical-or operation instead of the logical-and operation.
