Node.js es6 class support

Question

Finally es6 classes have landed in Node.js v4.0.0. But the feature needs --use_strict option to be passed. e.g.

node --use_strict sampleClass.js

What does this --use_strict option signify? Has it anything to do with "use strict"; javascript directive.

Note: On Linux Classes worked in v0.12 too but not in Windows

Edit: If you want to omit --use_strict flag than use "use strict"; in js file

@intekhab Node runs something called "magic mode" where it catches syntax errors in the REPL and tries to eval them with strict mode. — Benjamin Gruenbaum, Sep 16 '15 at 12:45

score 4 · Accepted Answer · edited May 23 '17 at 12:23

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Well, JS has a strict mode which slightly changes how scoping works as well as other small things. Generally, it should be preferred since the bodies of classes and modules are always in strict mode anyway.

Classes work both in strict and loose mode. However, the JavaScript engine Node runs only supports running classes in strict mode at the moment.

This is a limitation of V8 (the engine) and will be resolved in the future. Here is the bug tracking it.

edited May 23 '17 at 12:23

Community

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answered Sep 16 '15 at 12:44

Benjamin Gruenbaum

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so you mean --use_strict flag forces "use strict"; in code even if "use strict"; has not been explicitly mentioned – adnan kamili Sep 16 '15 at 12:52
@adnankamili yes, that's exactly what it does. – Benjamin Gruenbaum Sep 16 '15 at 12:53
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https://github.com/nodejs/node/blob/64beab0fc55f750bae648e9b69e027f2dbf3b18a/deps/v8/src/flag-definitions.h#L171 – Benjamin Gruenbaum Sep 16 '15 at 12:56

score 3 · Answer 2 · answered Mar 16 '19 at 07:54

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Starting from version 6, classes in NodeJS just work, so no --use_strict flag is required.

answered Mar 16 '19 at 07:54

jayarjo

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Node.js es6 class support

2 Answers2