javascript - hashing filenames in webpack - why? -

i came across following in webpack docs:

   {     output: {         path: path.join(__dirname, "assets", "[hash]"),         publicpath: "assets/[hash]/",         filename: "output.[hash].bundle.js",         chunkfilename: "[id].[hash].bundle.js"     } } 

what point/purpose of adding hash file names? docs talk alot how it, not why. scenarios in beneficial?

the reason cache busting / invalidation. people use query string (?somehash), doesn't work chunk splitting, while hash in filename does. see https://github.com/webpack/docs/wiki/long-term-caching overview.

note [chunkhash] cannot used on entry chunk if use require.ensure (or system.import in webpack 2)*; need separate "chunk manifest" entry chunk using chunk-manifest-webpack-plugin or inline-manifest-webpack-plugin.

*: in webpack 1, [chunkhash] cause entry chunk change if of "child chunks" changes unless split manifest out. in webpack 2, it'll compile time error.