JavaScript Object.prototype.toString 解析过程

在 JavaScript 规范（ECMA-262 19.1.3.6）中详细解释了

Object.prototype.toString

的解析过程：

this

undefined

"[object Undefined]"

this

null

"[object Null]"

O

ToObject(this)

isArray

IsArray(O)

isArray

isArray === true

builtinTag = "Array"

O

exotic

builtinTag = "String"

O

[[ParameterMap]]

builtinTag = "Arguments"

O

[[Call]]

builtinTag = "Function"

O

[[ErrorData]]

builtinTag = "Error"

O

[[BooleanData]]

builtinTag = "Boolean"

O

[[NumberData]]

builtinTag = "Number"

O

[[DateValue]]

builtinTag = "Date"

O

[[RegExpMather]]

builtinTag = "RegExp"

builtinTag = "Object"

tag

Get (O, @@toStringTag)

tag

Type(tag)

tag = builtinTag

"[object" + tag + "]"

[[Class]]