How Can I Set an Environment Variable as Gulp Task?

You can also define it as a script in your package.json

{
  "name": "myapp",
  "scripts": {
    "gulp": "NODE_ENV='development' gulp",
    "gulp-build": "NODE_ENV='production' gulp"
  },
  ...
}

And run it with npm run gulp-build. This has a few benefits

• You can define arguments easily instead of typing them every time
• Global gulp installation isn't required (same for other tools, like webpack)
• You can define multiple variants with different environment variables and(or) arguments without changing the gulpfile (as you can see above - gulp and gulp-build for development and production respectively)

Try gulp-env

Quick example on how to set some environment variables before running the nodemon task:

// gulpfile.js

var gulp = require('gulp');
var nodemon = require('nodemon');
var env = require('gulp-env');

gulp.task('nodemon', function() {
    // nodemon server (just an example task)
});

gulp.task('set-env', function () {
  env({
    vars: {
      MONGO_URI: "mongodb://localhost:27017/testdb-for-british-eyes-only",
      PORT: 9001
    }
  })
});

gulp.task('default', ['set-env', 'nodemon'])

You can Setup the environment like follows:

// Environment Setup
var env = process.env.NODE_ENV || 'development';

Then you can use the environment to process the code as follows:

gulp.task('js',function(){
gulp.src(jsPath)
.pipe(browserify({debug: env === 'development'}))
.pipe(gulpif(env === 'production' , uglify()))
.pipe(gulp.dest(jsDest));
});

You can also set one by default, and read the variables from a json file:

gulp.task('set-env', function () {
    var envId = gutil.env.env;
    if (!envId) {
      envId = "dev";
    }
    genv({
        file: "env." + envId + ".json"
    });
});

This would be always dev env by default, and you could call it setting another env, like this:

gulp --env prod

More of gulp-env