Stage 1 (Proposal)

What is it? A formal proposal for the feature.

What’s required? A so-called champion must be identified who is responsible for the proposal. Either the champion or a co-champion must be a member of TC39 (source). The problem solved by the proposal must be described in prose. The solution must be described via examples, an API and a discussion of semantics and algorithms. Lastly, potential obstacles for the proposal must be identified, such as interactions with other features and implementation challenges. Implementation-wise, polyfills and demos are needed.

What’s next? By accepting a proposal for stage 1, TC39 declares its willingness to examine, discuss and contribute to the proposal. Going forward, major changes to the proposal are expected.

These stage details are taken from Dr. Axel Rauschmayer's blog post. You can read more about the TC39 process in their official process document.

Pattern Matching
3979
Observable
2785
Partial application
940
Binary AST
879
Built In Modules (aka JS Standard Library)
825
do expressions
781
Slice notation
472
UUID
454
Operator overloading
349
First-class protocols
323
Getting last element of Array
303
export v from "mod"; statements
265
Asset References
249
Cancellation API
248
Number.range & BigInt.range
248
String.dedent
234
Decimal
229
Escaping Strings for RegExps
226
await operations
177
Block Params
165
Array filtering
161
SES (Secure EcmaScript)
150
JavaScript module fragments
147
Error stacks
140
Promise.try
130
Math.seededRandoms()
129
Collection methods
125
Array.prototype.unique()
112
Emitter
88
Extensions
86
"use module"
80
ArrayBuffer to/from Base64
77
async do expressions
76
class Access Expressions
75
Fixed shape objects
74
Generator arrow functions
71
Deep Path Properties in Record Literals
69
Extensible numeric literals
64
Declarations in Conditionals
62
Cryptographically Secure Random Number Generation
62
{BigInt,Number}.fromString
57
Object.freeze + Object.seal syntax
56
Array Equality
56
Maximally minimal mixins
54
defer module import eval
46
Math Extensions
44
Double-Ended Iterator and Destructuring
41
String.prototype.codePoints
38
Wavy Dot: Syntactic Support for Promise Pipelining
36
of and from on collection constructors
34
Compartments
33
Standardized Debug
30
IDL for ECMAScript
29
Richer Keys
27
Support for Distributed Promise Pipelining
27
Array.fromAsync
27
String.cooked
25
Private declarations
24
Readonly Collections
24
Evaluator Attributes
24
Module Keys
23
Dynamic Modules
23
Bind-this operator
22
uniform parsing of quasi-standard Date.parse input
20
BigInt Math
19
Get Intrinsic
16
new.initialize
15
Grouped Accessors and Auto-Accessors
14
Freezing prototypes
13
String is USV String
13
Intl LocaleMatcher
12
Dynamic Code Brand Checks
11
Modulus and Additional Integer Math
10
OOM Fails Fast
9
Reverse iteration
8
Preserve Host Virtualizability
8
Restrict subclassing support in built-in methods
8
Class Brand Checks
8
Smart Unit Preferences in Intl.NumberFormat
8
Math.signbit: IEEE-754 sign bit
6
RegExp Extended Mode and Comments
6
eraDisplay option for Intl.DateTimeFormat
6
Limited ArrayBuffer
5
Legacy reflection features for functions in JavaScript
3
RegExp \R Escape
3
RegExp Buffer Boundaries (\A, \z, \Z)
3
RegExp Modifiers
2
Float16 on TypedArrays, DataView, Math.hfround
Change Number.parseInt/parseFloat to not coerce null/undefined/NaN (repo link TBD)
Async initialization