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15 Best GulpJs Interview Questions and Answers

What Is Gulpjs?
Gulpjs is an open-source, build JavaScript task runner and very popularity toolkit for Automate and enhance complex tasks like magnification, checking js errors, unit testing, compile SASS, optimize images, bundling of various js and css files.

Gulpjs is very simple, automation, platform-agnostic, and strong ecosystem.

It’s used to solve the problems of code repetitions. It is easy to use, has a simple API, and is efficient.
There are only 4 APIs in gulp!          
1.      The gulp.task() - it used to define a task
2.      The gulp.src() - it used to read files in
3.      The gulp.dest ()- it used to write files out
4.      The gulp.watch() - it used to watch files for changes

You define a “task” in a file called “gulpfile.js” and task can be anything which you need to do repetitive.

The sample code for task, Gulpfile and Gruntfile –
The task looks like -
gulp.task('yourTask', function() {
  //do stuff
});

And gulpfile.js –
var gulp = require('gulp');
var gutil = require('gulp-util');

gulp.task('default', function(){
  // Default task code
});

And Gruntfile.js looks like –

module.exports = function(grunt) {
  //load all grunt tasks
  require('matchdep').filterDev('grunt-*').forEach(grunt.loadNpmTasks);

  grunt.initConfig({
    uglify: {
      dist: {
        src: ['assets/js/vendor/jquery.js', 'assets/js/vendor/**/*.js'],
        dest: "assets/js/vendor.min.js"
      }
    },
    sass: {
      options: {
        style: "expanded",
        lineNumbers: true
      },
      dist: {
        files: { 'assets/styles/application.css': 'assets/styles/application.scss' }
      }
    },
    watch: {
      scripts: {
        files: ['assets/js/**/*.js', '!assets/js/vendor.min.js'],
        tasks: ['uglify'],
        options: {
            spawn: false,
        },
      },
      css: {
        files: ['assets/styles/**/*.scss'],
        tasks: ['sass'],
        options: {
            spawn: false,
        }
      }
    }
  });

  grunt.registerTask('default', ['uglify', 'sass']);
};

Gulpjs is a JavaScript task runner that lets you automate tasks such as -
1.      Bundling and minifying libraries and style sheets
2.      Refreshing your browser when you save a file
3.      Quickly running unit tests
4.      Running code analysis
5.      Less/Sass to CSS compilation
6.      Copying modified files to an output directory

Is Gulpjs based on Node.js?
Yes!, Gulp is based on Node.js.

Why to use gulp?
1.      Gulp is open-source
2.      It is very faster
3.      Gulp plugins were designed to do a single job.
4.      GULP minify CSS, JS
5.      Compressing new and modified images
6.      Fast build
7.      Gulp used JavaScript configuration code that was less verbose, easier to read, simpler to modify, and provided better flexibility.

How do you install gulp?
Install gulp globally -
npm install --global gulp-cli


Install gulp in your project devDependencies -
npm install --save-dev gulp


Create a gulpfile.js at the root of your project - It looks like
gulp.task('default', function() {
  // place code for your default task here
});

Run gulp -
Gulp


How do you uninstall gulp?
Run following command to uninstall gulp globally -
npm uninstall -g gulp


Run following command to remove from your project -
npm uninstall --save-dev gulp


Which are different functions of a gulpfile?
The list gulpfile functions -
1.      Gulp.task
2.      Gulp.watch
3.      Gulp.src
4.      Gulp.dest

What is gulp.task function and how to use it?
The gulp.task is a function and used to define your tasks.

Example -
gulp.task('yourTask', function() {
  //do stuff
});

What is gulp.src function and how to use it?
The gulp.src is a function and used to points to your source files.

Example -
gulp.src(globs[, options])


What is gulp.dest function and how to use it?
The gulp.dest is a function and used to takes glob as parameter along with an optional [option] parameter.

Example -
gulp.dest(path[, options])


What is gulp.watch function and how to use it?
The gulp.dest is a function and used to watch changes automatically when you write code or modify your files.

Example -
gulp.task('watch', function () {
  // Watch .js files
 gulp.watch('src/js/*.js', ['scripts']);

  // Watch .scss files
 gulp.watch('src/scss/*.scss', ['sass']);
});

By Anil Singh | Rating of this article (*****)

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