└── README.md


/README.md:
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  1 | # REPL Goal for JS
  2 | 
  3 | For all examples, a single input passed to the REPL will be represented by lines prefixed by `> ` and output from the REPL will be represented by lines prefixed by `< `.
  4 | 
  5 | * [V8 Issue](https://bugs.chromium.org/p/v8/issues/detail?id=6903)
  6 | * [Related Node PR](https://github.com/nodejs/node/pull/17285)
  7 | 
  8 | ## Grammar Intentions
  9 | 
 10 | These are a list of intended usages with grammar examples, production mechanics will be done at a later time.
 11 | 
 12 | * Top Level Await
 13 | 
 14 | ```js
 15 | > Date.now() - await {then(f) {setTimeout(() => f(Date.now), 1000;)}}
 16 | < 1000
 17 | ```
 18 | 
 19 | * Reused environment record that removes conflicting bindings between evluations
 20 | 
 21 | ```js
 22 | > let x = 1; let y = 'a'; x
 23 | < 1
 24 | > let x = 2; x
 25 | < 2
 26 | > x
 27 | < 2
 28 | > y
 29 | < 'a'
 30 | ```
 31 | 
 32 | * `this` is the global
 33 | 
 34 | ```js
 35 | > typeof this
 36 | < "object"
 37 | > let x = 1; this.x
 38 | < undefined
 39 | ```
 40 | 
 41 | * Sloppy by default
 42 | 
 43 | ```js
 44 | > with ({x: 1}) x
 45 | < 1
 46 | > let x = 2; x
 47 | < 2
 48 | > eval('let x =3; x')
 49 | < 3
 50 | > x
 51 | < 3
 52 | ```
 53 | 
 54 | * Top level static import
 55 | 
 56 | ```js
 57 | > import {x} from './y';
 58 | < undefined
 59 | ```
 60 | 
 61 | * Object literal at start
 62 | 
 63 | ```js
 64 | > {x: 1}
 65 | < {"x": 1}
 66 | ```
 67 | 
 68 | * Strict mode DirectivePrologue
 69 | 
 70 | ```js
 71 | > "use strict"; with ({}) {}
 72 | < SyntaxError: Strict mode code may not include a with statement
 73 | ```
 74 | 
 75 | * REPL Environment Record is not Global Environment Record
 76 | 
 77 | ```js
 78 | > geval = eval; geval('let x = 1; x')
 79 | < 1
 80 | > let x = 2; x
 81 | < 2
 82 | > geval('x')
 83 | < 1
 84 | ```
 85 | 
 86 | ### Productions
 87 | 
 88 | ```
 89 | REPL Input :
 90 |   [lookahead = {] ObjectLiteral[+Await]
 91 |   [lookahead != {] Script[+Await, +Import]
 92 | 
 93 | ScriptBody:
 94 |   ScriptItemList[?Await, ?Import]
 95 | 
 96 | ScriptItemList:
 97 |   ScriptItem[?Await, ?Import]
 98 |   ScriptItemList ScriptItem[?Await, ?Import]
 99 | 
100 | ScriptItem:
101 |   if (+import) ImportDeclaration
102 |   StatementListItem[~Yield, ?Await, ?Import, ~Return]
103 | ```
104 | 
105 | ## Semantic Intentions
106 | 
107 | These are a list of intended spec changes by adding various things with new semantics.
108 | 
109 | 1. Allow the repeated running of lines from scrollback history.
110 | 
111 | Allow repeated running of the same input even if the input would collide with existing bindings on the REPL Environment Record.
112 | 
113 | 2. Abililty to remove bindings that have permanently been stuck in the Temporal Dead Zone.
114 | 
115 | Allow cleaning up of bindings that have become stuck in a TDZ.
116 | 
117 | 3. Separation from the global scope.
118 | 
119 | Allow a separation from the Global Environment in order to preserve logical consistency of how bindings work and giving a level of isolation to prevent leaving accidental bindings on the global when using tools such as a debugger.
120 | 
121 | ### REPL Lexical Environment
122 | 
123 | A Lexical Environment with an outer environment reference to a Global Lexical Environment. A REPL environment's Environment Record may be shared amongst multiple REPL Input Records.
124 | 
125 | ### REPL Input Record
126 | 
127 | A REPL Input Record encapsulates information about a repl input being evaluated. Each REPL Input Record contains the fields.
128 | 
129 | #### REPL Input Record Fields
130 | 
131 | Field Name | Value Type | Meaning
132 | ---- | ---- | ----
133 | [[Realm]]	Realm Record | undefined | The realm within which this REPL Input Record was created. undefined if not yet assigned.
134 | [[Environment]]	Lexical Environment | a REPL Lexical Environment | The Lexical Environment containing the top level bindings for this REPL Input Record. This field is set when the REPL Input Record is instantiated.
135 | [[ECMAScriptCode]] | a Parse Node | The result of parsing the source text of this module using REPL as the goal symbol.
136 | [[HostDefined]] | Any, default value is undefined. | Field reserved for use by host environments that need to associate additional information with a REPL Input Record.
137 | 
138 | ### REPL Environment Record
139 | 
140 | A REPL Environment Record is a declarative Environment Record that is used to represent the top-level scope of a REPL. It may be reused amongst multiple REPL Input Records.
141 | 
142 | ### ParseREPLInput ( sourceText, realm, REPLEnvironment, hostDefined )
143 | 
144 | Parses the sourceText and initializes all the lexical bindings declared in `sourceText` on a REPL Environment, removing them before hand if needed to avoid errors from bindings already being defined. All lexical bindings declared in `sourceText` may be deleted.
145 | 
146 | Returns a REPL Input Record.
147 | 
148 | ### REPL Input . Evaluate
149 | 
150 | Evaluates a REPL Input Record.
151 | 
152 | Returns a Promise to the Completion Value. 
153 | 


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