ES6默认参数？

Question

I'm trying to use default parameter values, but getting this error:

SyntaxError: Unexpected token =

Is this working in node now? I'm using 5.9.1

https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Functions/default_parameters

I also tried messing with passing flags to node without success.

  node --harmony_default_parameters

It seems like a basic part of ES6 so hope it would be working by now!

Answer 1

Is this working in node now?

Not yet. It's only available for testing under a flag. V8 v4.9 (released in Chrome 49) is the earliest stable version of V8 that supports default parameters. Nodejs v5.9.1 runs on top of V8 v4.6.85.31 . You can use the command node -p process.versions.v8 for checking the current V8 version. Also, you have to wait until Nodejs v6.x for a complete support of default parameters. You can see this issue for more details.

Answer 2

The problem seems to be a result of mixing ES6 style functions:

  getReply: (input, userId = null) => {   // No good

  getReply: function(input, userId = null) {  // OK

Answer 3

You can find the list of what ES6 features are currently supported by Node here . As it stands, it doesn't look like default paremeters are implemented, or at least not fully.