Espruino Feature List
What Follows is a table on JavaScript features and their implementation status in Espruino.
State is as follows:
-not implemented.YesimplementedOfficialimplemented, but only in boards that have enough memory. All Official Espruino Boards have these features.1vxximplemented in version1vxx
Summary
Espruino implements a large amount of the ES5 spec with parts of the ES6 spec where it is useful in an embedded environment.
Some features are left out intentionally where:
- It would be too costly to implement them (eg. Unicode Strings)
- They're generally considered bad practice (eg. labels)
Try Espruino for yourself online in the emulator
If you want a feature that isn't implemented you can vote on this GitHub issue
Any features not listed here, or differences in Espruino that users should be aware of? Please let us know!
General
| Feature | Implementation Status |
|---|---|
| Unicode Strings | - (8 bit strings only) |
| Regular Expressions | 1v95 Official (see below) |
| Labels | - |
Object.propertyIsEnumerable |
- |
with keyword |
- |
| Semicolon insertion on newlines | - return\n42; returns 42 in Espruino. |
| Function Hoisting | - |
Note: Espruino executes code by parsing as it executes. Function Hoisting wasn't implemented as it would require two passes, which would slow down execution.
ES5
List of ES5 features from http://kangax.github.io/compat-table/es5/
| ES5 Feature | Implementation Status |
|---|---|
| Strict Mode | - |
| Multiline String Literals | - |
| Accessors (Getters and Setters) | 2v00 Official |
| Trailing commas in object/array | Yes |
| Reserved words as property keys | Yes |
Reserved words as Identifiers (var of=1) |
- |
Object.create/defineProperty/defineProperties |
Yes |
Object.getPrototypeOf/keys |
Yes |
Object.seal/freeze/preventExtensions |
- |
Object.isSealed/isFrozen/isExtensible |
- |
Object.getOwnPropertyDescriptor/getOwnPropertyNames |
Yes |
Array.isArray |
Yes |
[].indexOf |
Yes |
[].lastIndexOf |
- |
[].every/some/forEach/map |
Official |
[].filter/reduce/reduceRight |
Official |
[].sort |
Yes |
String property access ("hi[0]`) |
Yes |
"".trim |
Yes |
Date.prototype.toISOString |
Yes |
Date.now() |
Yes |
Date.prototype.toJSON |
- |
Function.prototype.bind |
Yes |
JSON |
Yes |
unassignable undefined/NaN/Infinity |
Yes |
| Function.prototype.apply with non-arrays | Yes |
| parseInt ignores leading zeros | Yes |
| Function "prototype" non-enumerable | Yes |
| Arguments toStringTag is "Arguments" | - |
| Zero-width chars in identifiers | - |
Unreserved words, eg volatile |
Yes |
| Enumerable properties can be shadowed by non-enumerables | - |
| Thrown functions have proper "this" values | Yes |
ES6
List of ES6 features from http://es6-features.org:
| ES6 Feature | Implementation Status |
|---|---|
| Constants | 2v14 (const is parsed but treated like var in earlier FW) |
| Block scoped Functions/Variables | 2v14 (let is parsed but treated like var in earlier FW) |
| Arrow Functions | 1v88 Official |
| Default Parameter Values | - |
| Rest/Spread | - |
| Template Literals | 1v88 Official |
| Template Literal Raw String access | - |
| Binary/Octal Literals | Yes |
| Unicode String/RegExp | - |
| RegExp Sticky Matching | - |
| Enhanced Object Properties | 2v14 (methods) |
| Destructing Assignment | - |
Modules (import/export) |
- |
| Class Definition | 1v96 Official |
| Class Inheritance, Base Class Access | 1v96 Official |
| Class Inheritance from Expressions | - |
| Class Static Members | 1v96 Official |
| Class Getters/Setters | 2v00 Official |
| Symbol Type | - |
| Iterators | - |
| Generators | - |
| Map/Set/WeakMap/WeakSet | - |
| Typed Arrays | Yes |
Object.assign |
Yes |
[].findIndex |
2v00 Official |
"".repeat |
2v00 Official |
"".startsWith/endsWith/includes |
2v00 Official |
Number.isNaN/isFinite |
- (global isNaN/isFinite are implemented) |
Number.isSafeInteger |
- |
Number.EPSILON |
- |
Math.trunc |
- |
Math.sign |
2v16 |
| Promises | 1v86 Official |
| Promise Combination | 1v90 Official |
| Proxying / Reflection | - |
| Internationalization & Localization | - |
ES7/ES8 (2016/2017)
| ES7 Feature | Implementation Status |
|---|---|
Array.prototype.includes |
2v05 Official |
String.prototype.padStart/End |
2v08 Official |
Exponentiation Operator (**) |
- |
Exponentiation Assignment (**=) |
- |
| Async functions | - |
| Async generators | - |
Object.getOwnPropertyDescriptors |
2v17 |
Object.values/Object.entries |
2v14 |
| Typed Objects | - |
| Trailing commas in function syntax | - |
| Object rest/spread properties | - |
ES9/ES10 (2018/2019)
| ES9/ES10 Feature | Implementation Status |
|---|---|
| Asynchronous Iteration | - |
Promise.finally |
- |
| Object Rest Properties | - |
New RegExp Features |
- |
String.trimStart() |
- |
String.trimEnd() |
- |
Object.fromEntries |
2v17 |
| Optional catch binding | 2v20 |
Array.flat() |
- |
Array.flatMap() |
- |
Revised Array.sort() |
No - uses quicksort |
Revised JSON.stringify() |
UTF8-enabled builds |
| Separator symbols allowed in string literals | UTF8-enabled builds |
ES2020
| ES2020 Feature | Implementation Status | ||
|---|---|---|---|
BigInt |
- | ||
String.matchAll() |
- | ||
The Nullish Coalescing Operator (??) |
2v14 |
||
The Optional Chaining Operator (?.) |
PR | ||
Logical AND Assignment Operator (&&=) |
- | ||
| Logical OR Assignment (` | =`) | - | |
Nullish Coalescing Assignment (??=) |
- | ||
Promise allSettled() |
- | ||
| Dynamic Import | - |
ES2021
| Promise.any() | - |
| String.replaceAll() | - |
| Numeric Separators (_) | 2v14 |
Regular Expressions
Espruino aims to support most commonly used RegExp contructs, however some parts of the spec are not implemented:
- Assertions other than
^and$ - Numeric quantifiers (eg
x{3})
There's a GitHub issue concerning RegExp features here
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