ECMAScript (ES)
- standard of language
- beware: doesn’t contain Web APIs, i.e. doesn’t have any side effects
- “JavaScript” is trademark of Oracle, has no relation with Java except historic name to attract popularity
- dynamic typing, prototype-based inheritance, first-class functions
ECMAScript versions
| ES (ECMAScript) |
year |
|---|
| ES1 |
1997 |
| ES2 |
1998 |
| ES3 |
1999 |
| ES4 |
abandoned |
| ES5 |
2009 |
| ES6 / ES2015 |
2015 |
| ES2016 |
2016 |
| ES2017 |
2017 |
| ES2018 |
2018 |
| ES2019 |
2019 |
| ES2020 |
2020 |
| ES[year] |
[year] |
- feature gap: gap of current ES version to ES version supported by runtime environment
- use transpiler to bridge feature gap, supporting old runtime environment shouldn’t come at the expense of the developer, developer needs to be able to use contemporary features
Implementation
- usually just-in-time compiled, first parsed (catches static errors like syntax, builds scope, etc.), then executed
- modern runtimes use Mark-and-sweep garbage collection, old ones used Reference-counting garbage collection
Resources