- It is extremely fast. Validating three.js (800 KB source) takes less than a second on a modern machine.
- It looks only for syntax errors, it does not care about coding style at all.
- It handles generated files as the result of minification or compilation (CoffeeScript, Dart, TypeScript, etc).
- It tries to be tolerant and not give up immediately on the first error, especially for strict mode violations.
Esprima is available as an npm package, so installing it only takes a second:
sudo npm install -g esprima
Using Esprima from the command line is simple:
The only thing to note about running from the command line: if the validation succeeds, you won’t get much in the way of confirmation. Which can be painful if you are processing a whole directory. You only get useful feedback in the default mode on error.
However, if you don’t mind reading a little XML:
esvalidate lib/*.js --format=junit
Prints junit XML which at least you can visually parse to see which files were validated.
Where would I use this where I might not use JsHint? As a pre-commit hook to screen my checkins. Instead of going through a check-in, building everything, then running JSHint just to hear that something is not up to spec, I can add a little script that will do a quick sanity check of my JS before I go to commit anything to git.
If you’ve never created a pre-commit hook before, it’s pretty easy. Two lines in bash will give you a pre-commit file:
chmod +x .git/hooks/pre-commit
This is windows version of the code for the pre-commit hook:
files=$(git diff-index --name-only HEAD | grep -l '\.js$')
for file in $files; do
if [ $? -eq 1 ]; then
echo "Syntax error: $file"
To make this work on Linux, just remove the remove the #!/bin/sh line.
For more information about Esprima, check out this article by the author.