Can you pass a Grunt variable to a JavaScript function within a Grunt task?

Question

Here is an example of what I'm looking for:

module.exports = function(grunt) {
  grunt.initConfig({

    config: grunt.file.readYAML('_config.yml'),
    // example variable: <%= config.scripts %>

    copy: {
      scripts: (function() {
        if (config.scripts === true) { // I want to target <%= config.scripts %>
          return {
            expand: true,
            cwd: '<%= input %>/_assets/js/',
            src: '**/*.js',
            dest: '<%= output %>/assets/js/'
          };
        } else {
          return {
            // do nothing
          };
        }
      })()
    }

  });
};

I know Grunt can read the data from within a file using 'grunt.file.readJSON', and then have that data available with the following type of variable, '<%= pkg.value %>'.

What I'm wanting to do is to create a task with if/else options based on the variables from within the JSON file. What I'm unclear on is how to pass a Grunt variable '<%= pkg.value %>' into the JavaScript if statement in a way that it understands. I've tried passing it in the same Grunt format with '<%= %>', as well as stripping that part away and passing 'pkg.value', but neither seems to work.

If someone can shed some light on whether or not this can be done and how, I would greatly appreciate it. Thanks!

Answer 1

Instead of directly assign the grunt config in config attribute, store it in a variable (gruntConfig). Now you will be able to access it in the following code.

module.exports = function(grunt) {
    // store your grunt config
    var gruntConfig = grunt.file.readYAML('_config.yml');
    // init `script` with an empty object
    var script = {};
    if (gruntConfig.script) {
        script = {
            expand: true,
            cwd: '<%= input %>/_assets/js/',
            src: '**/*.js',
            dest: '<%= output %>/assets/js/'
        };
    }
    // Init Grunt configuration
    grunt.initConfig({
        config: gruntConfig,
        copy: {
            scripts: script
        }
    });
};

Answer 2

When I have more time, I'll probably look into some additional ideas, but based on the ideas offered here, this is what I ended up going with for now.

module.exports = function(grunt) {

  var config = grunt.file.readYAML('_config.yml');

  grunt.initConfig({

    copy: {
      scripts: (function() {
        if (config.scripts) {
          return {
            expand: true,
            cwd: 'input/_assets/js/',
            src: '**/*.js',
            dest: 'output/assets/js/'
          };
        } else {
          return {
            // do nothing
          };
        }
      })()
    }

  });
};

Thanks, everyone, for your help!