gulpfile.js

const gulp = require('gulp');
const eslint = require('gulp-eslint');
const gulpIf = require('gulp-if');

function isFixed(file) {
    // Has ESLint fixed the file contents?
    return file.eslint != null && file.eslint.fixed;
}

gulp.task('lint', () => {
    // ESLint ignores files with "node_modules" paths.
    // So, it's best to have gulp ignore the directory as well.
    // Also, Be sure to return the stream from the task;
    // Otherwise, the task may end before the stream has finished.
    return gulp.src(['./**/*.js', '!node_modules/**'])
    // eslint() attaches the lint output to the "eslint" property
    // of the file object so it can be used by other modules.
        .pipe(eslint())
        // eslint.format() outputs the lint results to the console.
        // Alternatively use eslint.formatEach() (see Docs).
        .pipe(eslint.format())
        // To have the process exit with an error code (1) on
        // lint error, return the stream and pipe to failAfterError last.
        .pipe(eslint.failAfterError());
});

gulp.task('lint-and-fix', () => {
    return gulp.src(['./**/*.js', '!node_modules/**'])
    // eslint() attaches the lint output to the "eslint" property
    // of the file object so it can be used by other modules.
        .pipe(
            eslint({ fix: true })
        )
        // eslint.format() outputs the lint results to the console.
        // Alternatively use eslint.formatEach() (see Docs).
        .pipe(
            eslint.format()
        )
        .pipe(
            gulpIf(
                isFixed, gulp.dest('./')
            )
        );
});