how to concat all my js files in src/script (with js files inside of it and fils in each subdir) ? The output is x3 ....

gistfile1.txt

       module.exports = function(grunt) {
    // Project configuration.
    grunt.initConfig({
        pkg: grunt.file.readJSON('package.json'),
        clean: {
            build: {
                src: ['build']
            }
        },
        copy: {
            assets: {
                files: [{
                    expand: true,
                    cwd: 'src/img/',
                    src: ['**'],
                    dest: 'build/img/'
                }, {
                    expand: true,
                    cwd: 'src/templates/',
                    src: ['**'],
                    dest: 'build/templates/'
                }, {
                    expand: true,
                    cwd: 'src/css/',
                    src: ['**', '!*.less'],
                    dest: 'build/css/'
                }, {
                    expand: true,
                    cwd: 'src/vendor/',
                    src: ['**'],
                    dest: 'build/vendor/'
                }, ]
            }
        },
        processhtml: {
            dist: {
                files: {
                    'build/index.html': ['src/index.html']
                }
            }
        },
        uglify: {
            options: {
                report: 'min',
                banner: '/*! <%= pkg.name %> <%= grunt.template.today("yyyy-mm-dd") %> */\n',

            },
            build: {
                src: 'build/script/',
                dest: 'build/script/app.min.js',
            }
        },
        concat: {
            build: {
                src: ['src/script/**/*.js'],
                dest: 'build/script/app2.js'
            }
        },
        cssmin: {
            build: {
                files: {}
            }
        },
        ngmin: {
            dist: {
                files: [{
                    expand: true,
                    cwd: 'src/script',
                    src: ['**/*.js'],
                    dest: 'build/script'
                }]
            }
        },
        less: {
            development: {
                options: {
                    report: 'min',
                },
                src: 'src/css/styles.less',
                dest: 'build/css/styles.css',
            },
        },
        htmlbuild: {
            build: {
                src: 'src/index.html',
                dest: 'build/index.html',
                options: {}
            },
        },
    });

    grunt.loadNpmTasks('grunt-contrib-less');
    grunt.loadNpmTasks('grunt-contrib-concat');
    grunt.loadNpmTasks('grunt-contrib-clean');
    grunt.loadNpmTasks('grunt-contrib-uglify');
    grunt.loadNpmTasks('grunt-ngmin');
    grunt.loadNpmTasks('grunt-html-build');
    grunt.loadNpmTasks('grunt-processhtml');
    grunt.loadNpmTasks('grunt-contrib-copy');
    grunt.loadNpmTasks('grunt-contrib-connect');

    // Default task(s).
    grunt.registerTask('default', ['clean', 'copy', 'processhtml', 'concat']);
};