Using Webpack, I get a load of warnings from UglifyJSPlugin for all my 3rd party code.
Is it possible to turn off warnings for some libraries only?
No, it's currently only possible to turn off all warnings, per the UglifyJS compressor options: https://github.com/mishoo/UglifyJS2#compressor-options
You can turn off all warnings by passing UglifyJS options to the constructor for Webpack's UglifyJsPlugin: https://webpack.github.io/docs/list-of-plugins.html#uglifyjsplugin
In your webpack.config.js, you'd need to have something like:
var webpack = require('webpack');
module.exports = {
...
plugins: [
new webpack.optimize.UglifyJsPlugin({
compress: {
warnings: false
}
})
]
}