How can I check JavaScript code for syntax errors ONLY from the command line?

Question

JavaScript programs can be checked for errors in IDEs or using online web apps but I'm looking for a way to detect syntax errors alone.

I've tried JSLint and JSHint and looked at their options but I haven't been able to find a combination that would exclude warnings and just shows the syntax errors.

How do I check JavaScript code for syntax errors only from the command line?

@DanDascalescu Than set up the validation rules to the way you want! jslint.com/lint.html#options — epascarello
– epascarello, Commented Feb 18, 2014 at 14:47
@epascarello: Do you know which combination of JSLint options will only output syntax errors? — Dan Dascalescu
– Dan Dascalescu, Commented Feb 19, 2014 at 5:13
Here is the meta discussion about whether this question should be re-opened. — George Stocker
– George Stocker, Commented Feb 24, 2014 at 16:08
If you know JavaScript well, you can simply edit/fork JSLint and make it do what you want. Not as daunting as it sounds. The code is very clean. This question has been asked before iirc; you might find your errors-only JSLint project is pretty popular. — ruffin
– ruffin, Commented Feb 25, 2014 at 12:09

kenorb · Accepted Answer · 2017-07-24 13:48:57Z

33

I use acorn:

$ acorn --silent tests/files/js-error.js; echo $?
Unexpected token (1:14)
1

$ acorn --silent tests/files/js-ok.js; echo $?
0

Install via: npm -g install acorn.

edited Jul 24, 2017 at 13:48

kenorb

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answered Jun 24, 2014 at 11:52

cweiske

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2 Comments

Alex Over a year ago

acorn does not seen to work for me: Error: Cannot find module './_acorn.js'

ACK_stoverflow Over a year ago

Also installable in debian with apt install node-acorn

Dan Dascalescu · Accepted Answer · 2014-04-02 22:11:11Z

19

The solution is to enable jshint's --verbose option, which shows the error or warning code (e.g. E020 for Expected '}' to match '{' or W110 for Mixed double and single quotes), then grep for errors only:

jshint --verbose test.js | grep -E E[0-9]+.$

answered Apr 2, 2014 at 22:11

Dan Dascalescu

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3 Comments

mynameistechno Over a year ago

If there are too many warnings and errors though you end up getting a "too many errors, quitting" message. You need to set a config file option such as maxerr:10000 to avoid this, which is not ideal.

Cameron Hurd Over a year ago

@mynameistechno, you could also add --maxerr 10000 when calling it from the command line, as the answer seems to already imply.

erjiang Over a year ago

jshint 2.9.4 doesn't seem to take a "--maxerr" argument - was it removed?

idmean · Accepted Answer · 2014-02-18 14:08:21Z

5

JSHint does what you want. http://www.jshint.com/

You can configure which warnings or errors to show.

An example:

$ jshint myfile.js
myfile.js: line 10, col 39, Octal literals are not allowed in strict mode.

1 error

answered Feb 18, 2014 at 14:08

idmean

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3 Comments

Dan Dascalescu Over a year ago

How do I configure it to show only syntax errors, not warnings?

cweiske Over a year ago

currently it's not possible to disable all warnings in jshint. You have to do it one by one in a config file :/

John Langford Over a year ago

On Mac OSX, this can be installed using: npm install -g jshint

Ahsan · Accepted Answer · 2021-10-05 13:23:31Z

5

You could use node's built-in syntax checking option:

node --check filename.js

Ref: https://nodejs.org/api/cli.html#cli_c_check

answered Oct 5, 2021 at 13:23

Ahsan

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Comments

ernesto · Accepted Answer · 2015-07-30 12:28:42Z

3

Any JavaScript parser should do, acorn mentioned by @cweise is nice because it is fast and has a --silent switch.

You could also use esvalidate from the npm esprima package: http://ariya.ofilabs.com/2012/10/javascript-validator-with-esprima.html

$ npm install -g esprima
$ esvalidate js-file-with-errors.js 
js-file-with-errors.js:1: Invalid left-hand side in assignment

answered Jul 30, 2015 at 12:28

ernesto

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Comments

mirza · Accepted Answer · 2017-06-30 22:33:52Z

Here is an answer for a Continuous Integration scenario.

1- Checks all the JavaScript files with exclude folder, subfolder and file features.

2- Exit if there is an error.

esvalidate --version || npm install -g esprima;
find ./ -not \( -path ./exclude_folder_1 -prune \) -not \( -path ./exclude/sub_folder -prune \) -not \( -path ./exclude/sub_folder_2 -prune \) ! -name exclude_specified_file.js  -name \*.js -exec esvalidate '{}' \; | grep -v "No syntax errors detected" && echo "Javascript Syntax error(s) detected" && exit 1;

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