javascript - gulp-concat twice the content -

that's weird thing me, have task concat .js files , uglify them watcher, concat task twice content in every call...

here gulpfile:

'use strict';  let gulp        = require('gulp'); let stylus      = require('gulp-stylus'); let sourcemaps  = require('gulp-sourcemaps'); let concat      = require('gulp-concat'); let uglify      = require('gulp-uglify'); let plumber     = require('gulp-plumber'); let bootstrap   = require('bootstrap-styl'); let rupture     = require('rupture'); let copy        = require('gulp-copy2');  /*   prepare paths */ let base = './theme'; let themename = 'own-theme';  let paths = {   stylus    : `${base}/${themename}/css`,   js        : `${base}/${themename}/js`,   vendor    : `${base}/${themename}/js/vendor` }  /*   stylus compile */ gulp.task('stylus-compile', () => {   return gulp.src([`${paths.stylus}/dev/*.styl`, `${paths.stylus}/!**/_*.styl`])     .pipe(plumber())     .pipe(stylus({       use: [bootstrap(), rupture()],       compress: true     }))     .pipe(sourcemaps.write('./'))     .pipe(gulp.dest(`${paths.stylus}`)); });  /*   bootstrap-styl js files , concat/uglify them */  gulp.task('bootstrap-build', () => {   return gulp.src([     'node_modules/bootstrap-styl/js/transition.js',     'node_modules/bootstrap-styl/js/alert.js',     'node_modules/bootstrap-styl/js/button.js',     'node_modules/bootstrap-styl/js/carousel.js',     'node_modules/bootstrap-styl/js/collapse.js',     'node_modules/bootstrap-styl/js/dropdown.js',     'node_modules/bootstrap-styl/js/modal.js',     'node_modules/bootstrap-styl/js/tooltip.js',     'node_modules/bootstrap-styl/js/popover.js',     'node_modules/bootstrap-styl/js/scrollspy.js',     'node_modules/bootstrap-styl/js/tab.js',     'node_modules/bootstrap-styl/js/affix.js'   ])   .pipe(sourcemaps.init())   .pipe(concat('bootstrap.min.js'))   .pipe(uglify())   .pipe(sourcemaps.write('./'))   .pipe(gulp.dest(`${paths.vendor}`));  });  /*   js assets npm */ gulp.task('js-copy', () => {   let dirs = [     { src: 'node_modules/jquery/dist/jquery.min.js', dest: `${paths.vendor}/jquery.min.js` },     { src: 'node_modules/sweet-scroll/sweet-scroll.min.js', dest: `${paths.vendor}/sweet-scroll.min.js` }   ]     return copy(dirs); });  /*   concat/uglify js files */ gulp.task('js-build', () => { return gulp.src(`${paths.js}/*.js`)   .pipe(sourcemaps.init())   .pipe(concat('site.min.js'))   // .pipe(uglify())   .pipe(sourcemaps.write('./'))   .pipe(gulp.dest(`${paths.js}`)); })  /*   watch */ gulp.task('watch', () => {   gulp.watch(`${paths.js}/*.js`, ['js-build']);   gulp.watch(`${paths.stylus}/dev/*.styl`, ['stylus-compile']); });  gulp.task('default', ['bootstrap-build', 'js-copy', 'watch']); 

the bootstrap-build task don't twice content no matter how many times call task, js-build does.

here test separated scripts concat , results:

file 1:

(function() {    console.log("oh!")   console.log("uh!")  }).call(this); 

file 2:

(function() {   console.log("hey") }).call(this); 

concated file(uh, oh file re-saved after watcher fired):

(function() {    console.log("oh!")   console.log("uh!")  }).call(this); (function() {    console.log("oh!")   console.log("uh!")  }).call(this); (function() {   console.log("hey") }).call(this); //# sourcemappingurl=site.min.js.map  (function() {   console.log("hey") }).call(this); //# sourcemappingurl=site.min.js.map 

in every re-save, concat twice content... don't problem. idea?

thanks in adnvance.

the reason bootstrap-build works because places resulting bootstrap.min.js in different folder source files.

your js-build task concatenates .js files in path.js folder , places resulting site.min.js in same folder.

that means when first running js-build files file1.js , file2.js concatenated site.min.js. on second run files file1.js, file2.js , site.min.js concatenated site.min.js. every time run js-build task site.min.js grows.

what need exclude site.min.js being concatenated other files:

gulp.task('js-build', () => {   return gulp.src([       `${paths.js}/*.js`,       `!${paths.js}/site.min.js`     ])     .pipe(sourcemaps.init())     .pipe(concat('site.min.js'))     // .pipe(uglify())     .pipe(sourcemaps.write('./'))     .pipe(gulp.dest(`${paths.js}`)); })