gulp-has

Optimize code paths using has API feature detection.

Installation

Install package with NPM and add it to your development dependencies:

npm install --save-dev gulp-has

Usage

var has = require( 'gulp-has' ),
    uglify = require( 'gulp-uglify' );

gulp.task( 'compress', function(){
    gulp.src( 'lib/*.js' )
        .pipe( has( {
            // Build for environment that has Object.create
            'object-create': true
        } ) )
        .pipe( uglify( {
            compress: {
                // Discard unreachable code
                dead_code: true
            }
        } ) )
        .pipe( gulp.dest( 'dist' ) );
} );

When run against code written like this:

if( !has( 'object-create' ) ){
    Object.create = ( function(){
        var Temp = function(){};
        return function( prototype ){
            if( arguments.length > 1 ){
                throw Error( 'Second argument not supported' );
            }
            if( typeof prototype != 'object' ){
                throw TypeError( 'Argument must be an object' );
            }
            
            Temp.prototype = prototype;
            var result = new Temp();
            Temp.prototype = null;
            
            return result;
        };
    } )();
}

var o = Object.create( null );

The compress task would transform it into something like this:

var o = Object.create( null );

has API

The has API was introduced by has.js as a convention for doing feature detection; however you don't need to use has.js to take advantage of gulp-has.

// A small adapter for Modernizr
function has( id ){
    return Modernizr[ id ];
}

if( has( 'canvas' ) ){
    console.log( 'This browser supports canvas.' );
} else {
    console.log( 'No canvas.' );
}