How to fix unexpected token in ESLint?

user_3818576 0
Viewed 6432

I install ESLint globally using the command npm install -g eslint on my Mac. It was successful installing, but when I run eslint -v this is the issue I encounter:

$ npm install -g eslint
path/to/bin/eslint -> path/to/lib/node_modules/eslint/bin/eslint.js
+ eslint@7.3.1
added 107 packages from 63 contributors in 4.823s

$ eslint -v
path/to/lib/node_modules/eslint/bin/eslint.js:93
        } catch {
                ^

SyntaxError: Unexpected token {
    at createScript (vm.js:80:10)
    at Object.runInThisContext (vm.js:139:10)
    at Module._compile (module.js:617:28)
    at Object.Module._extensions..js (module.js:664:10)
    at Module.load (module.js:566:32)
    at tryModuleLoad (module.js:506:12)
    at Function.Module._load (module.js:498:3)
    at Function.Module.runMain (module.js:694:10)
    at startup (bootstrap_node.js:204:16)
    at bootstrap_node.js:625:3

I would like to know what are the missing steps that cause this issue? I'm using Node.js v8.16.2 and NPM v6.4.1.

npm eslint
2 Answers

The error happens because } catch { is a relatively recent (ES2019) language feature called "optional catch binding"; prior to its introduction, binding the caught error (e.g. } catch (err) {) was required syntactically. Per node.green, you need at least Node 10 to have that language feature.

So why does this happen in ESLint? Per e.g. the release blog, version 7 has dropped support for Node 8; they're no longer testing against that version and more modern language features will be assumed to be supported.

To fix it, either:

  1. Upgrade Node (Node 8 is out of LTS, which is why ESLint dropped support); or
  2. npm install eslint@6 (with -g if you want to install globally) to use the older version of ESLint with Node 8 support.
user_30017610

In case it's helpful for anyone, I had a slightly different twist on the other answer. In my case, the error was happening during the Travis CI build process and causing it to fail. The solution in my case was to update my .travis.yml file to node_js: "16"

user_110724180
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