ES5 Study
Keywords
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break
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do
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instanceof
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typeof
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case
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else
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new
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var
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catch
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finally
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return
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void
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continue
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for
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switch
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while
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debugger
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function
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this
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with
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default
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if
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throw
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delete
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in
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try
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Future Reserved words
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class
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enum
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extends
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super
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const
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export
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import
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implements
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let
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private
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public
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yield
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interface
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package
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protected
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static
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ECMAScript language types: Undefined, Null, Boolean, String, Number and Object.
A specification type corresponds to meta-values that are used within algorithms to describe the semantics of ECMAScript language constructs and ECMAScript language types. The specification types are Reference, List, Completion, Property Descriptor, Property Identifier, Lexical Environment, and Environment Record. Specification type used to describe intermediate results of EScript expression evaluation, but cannot be stored as properties of objects or values of EScript language variables.
Undefined Type-undefined,
Null Type - null,
Boolean Type - true or false,
String Type - set of all finite ordered sequences of zero or more 16-bit unsigned integer values("elements").
Number Type - NaN, +Infinity(Infinity), -Infinity, +0(0), -0,
Object Type - a collection of properties. Each property is either a named data property, a named accessor property, or an internal property.
data property: associates a name with an ECMAScript language value and a set of Boolean attributes
accessor property: associates a name with one or two accessor functions, and a set of Boolean attributes. It used to store or retrieve an ECMAScript language value that is associated with the property.
internal property: has no name and is not directly accessible via EScript language operators. It exist purely for specification purposes.
Two kinds of access for named(non-internal) properties: get and put, corresponding to retrieval and assignment, respectively.
Attributes of a Named Data Property:
[[Value]], [[Writable]], [Enumerable]], [[Configurable]]
Attributes of a Named Accessor Property:
[[Get]], [[Set]], [[Enumerable]], [[Configurable]]
Default Attribute Values:
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Attribute Name
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Default Value
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[[Value]]
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undefined
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[[Get]]
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undefined
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[[Set]]
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undefined
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[[Writable]]
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false
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[[Enumerable]]
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false
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[[Configurable]]
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false
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