Gruntjs looping a grunt 'copy file' task - node.js

Question

I'm trying to copy an index.html file to multiple folders. I've been looking on stack overflow and almost found the solution i'm looking for. The loop in my example only copy's the index.html file to the last folder of the folders array. I wonder what i'm overlooking. any ideas?
module.exports = function(grunt){
grunt.initConfig({
copy:{
files:{
flatten:true,
expand: false,
src: [
'scaffold/index.html',
],
dest: "dist/<%= grunt.option('folder') %>/",
filter: 'isFile',
force: true
}
}
})
function copytoFolders() {
var folders = ["300x600", "300x250", "336x280"], folder;
for (folder in folders)
{
grunt.option('folder', folders[folder]);
grunt.task.run('copy');
}
}
grunt.loadNpmTasks('grunt-contrib-copy-force');
grunt.registerTask('copyFol', copytoFolders)
}

Answer 1

Ok i solved it by looking at this post:
stack overflow post
So basically it now returns a file object array and when the default task is called, it executes the object files.
Here is the script that works for me:
module.exports = function(grunt) {
function getFiles() {
var folders = ["300x600", "300x250", "336x280"];
var files = [];
for (var folder in folders) {
files.push({
flatten:true,
expand: true,
src: [
'scaffold/index.html',
],
dest: "dist/" + folders[folder] + "/",
filter: 'isFile'
});
}
return files;
}
grunt.initConfig({
copy: {
core: {
files: getFiles()
}
}
});
grunt.loadNpmTasks('grunt-contrib-copy');
grunt.registerTask('default', ['copy:core']);
};