neff v1.5.0
Neff is simple express middleware for handling feature flags.
Usage
The standard way to use neff on the client & the server side is to check for enabled features using the isEnabled() API.
var users = 500;
var moreUsers = neff.isEnabled("moreUsers");
if (moreUsers) {
users++;
}Argument-Based Config
To get started with neff you'll want to make sure you call neff, passing it an object with feature names and either true or false values.
var neff = require("neff")({
"feature1": true,
"feature2": false
});
app.use(neff);NConf-Based Config
If you'd like to utilize NConf for this, you can reference an NConf JSON file and my config looks like this:
"features": {
"feature1": true,
"feature2": false
}Then pass the config object for the features to neff:
var neff = require("neff")(nconf.get('features'));
app.use(neff);Accessing in templates
The first thing it allows you to do is access feature flags directly in your template such as (dust syntax):
{?feature-feature1}
MY HIDDDEN CODE
{/feature-feature1}Express Router Limiter
This route is only available when the feature flag is enabled. Otherwise the user would see a server error page.
var neff = require("neff");
app.get("/myhidden/route", neff.limit("feature1"), function(req, res) {
res.send("You have found feature1!");
});Client Side Usage
It also provides a string of class names you can insert into your <body> (dust syntax):
<body class="{featureClasses}">The output prepends feature- to the classname, so you might see something like <body class="feature-feature1"> with the config above. Only enabled features show up in the string.
Make sure your features are declared on your DOM like so:
<body class="feature-feature1 feature-feature2">Once you've done that you can take advantage of the flags in 2 ways.
CSS
/* Create a block that's hidden by default */
.my-cool-block {
display: none;
}
/* Display that block when your flag is present */
.feature-feature1 .my-cool-block {
display: block;
}JavaScript
define(["neff"], function(neff) {
if (neff.isEnabled("feature1")) {
/* .. */
}
});Thanks
Inspired heavily by https://npmjs.org/package/feature-gateway.