ecmascript-5

Consider this: var a = {}, b = a; In terms of the spec, b = a boils down to PutValue(b, GetValue(a)) , right? And GetValue(a) uses GetBindingValue("a", strictFlag) abstract operation, which returns "the value" in a . And "the value" is "the object" originally assigned to a . Then "the object" is stored in b , just like any other value would. But what is "the object" precisely? Where does the specification say that values of the Object type behave differently than primitives? Is it only that primitives are immutable, and objects are mutable? I'm asking because we always talk about "object

I'm fairly new to javascript, but I'm in love with it's dangerously fast and loose expressiveness. That said, I noticed that apparently when operating in "use strict" mode, you can't delete objects. I'm not a huge fan of deleting things (since, in theory, scope should take care of that anyway), but I wonder what was the motivation behind removing this feature? The delete statement is still allowed in strict mode, but some particular uses of it are erroneous. It's only allowed for object properties, not simple names, and only for object properties that can be deleted. Thus var a = {x: 0};

Consider the following excerpt from ECMA-262 v5.1 (which I recently saw in this question ): A Lexical Environment is a specification type used to define the association of Identifiers to specific variables and functions based upon the lexical nesting structure of ECMAScript code. A Lexical Environment consists of an Environment Record and a possibly null reference to an outer Lexical Environment. Usually a Lexical Environment is associated with some specific syntactic structure of ECMAScript code such as a FunctionDeclaration, a WithStatement, or a Catch clause of a TryStatement and a new