hapi will automatically generate ETag headers for your responses when you use the file handler or reply.file() method. But if you're using any other kind of response (such as JSON, HTML, text etc) you won't get ETags for free. This plugin fixes that!

##Installation and configuration

To install, just add to your npm deps:

npm install --save hapi-etags

Then register the plugin:

server.register([
    {
        register: require('hapi-etags'),
        options: {
			// explained below
        }
    }
], function (err) {

    if (err) {
        throw err;
    }

    server.start(function () {
        console.log('Started!');
    });

});

The following options are available when registering the plugin [defaults]:

• algo - The hashing function to use to calculate the ETag. Can be anything in Crypto.getHashes() Default: sha1
• encoding - The encoding to use for the ETag hash. Can be base64 or hex. Default: 'base64'
• varieties - A list of the variety types that the plugin will calculate etags for. Options are ['plain', 'buffer', 'view', 'stream']. Default: ['plain', 'buffer']
• etagOptions - The same options argument that's passed to response.etag (http://hapijs.com/api#response-object-redirect-methods). Default: {}

##Advice and warnings

Only the plain and buffer varieties are set by default. Support for the other varieties should be considered experimental. Here's some issues to be aware of:

• view - Has to pre-render the view template to calculate the ETag so a performance hit will be taken.
• stream - Has to read and buffer the entire stream data into memory to calculate the ETag. Clients could be waiting while this happens. Could totally break the responsiveness of your app - beware! Only makes sense to use this when your clients have bandwidth limitations and you're willing to go to extreme lengths to prevent them redownloading streamed content.