Gulp loop from json file

You can build some function that handle an array of plugin/type to filter those which are needed :

[{
    "plugin": "plugin_a_name",
    "types": ["js"]
}, {
    "plugin": "plugin_b_name"
}]

In the above sub-config, it will only copy JS file for plugin_a and all the types (JS/CSS) for plugin_b.

You can then iterate over all the filtered plugin/types and grab them from your config path.json file if existing :

var gulp = require('gulp'),
    config = require('./path.json');

function copyTask(target) {
    //iterate over config files for the specified type
    for (src in target) {
        console.log("copy from " + src + " to " + target[src]);
        gulp.src(src).pipe(gulp.dest(target[src]));
    }
}

function copyFilter(pluginFilter) {
    //loop on filter
    for (var obj in pluginFilter) {
        var pluginVal = pluginFilter[obj];
        //check config has plugin
        if (config[pluginVal.plugin]) {
            if (pluginVal.types) {
                //loop on type type filter
                for (var type in pluginVal.types) {
                    var typeVal = pluginVal.types[type];
                    // check config has type
                    if (config[pluginVal.plugin][typeVal]) {
                        copyTask(config[pluginVal.plugin][typeVal]);
                    } else {
                        console.log("type " + typeVal + " not found for plugin " + pluginVal.plugin);
                    }
                }
            } else {
                //iterate over all the types here
                for (type in config[pluginVal.plugin]) {
                    copyTask(config[pluginVal.plugin][type]);
                }
            }
        } else {
            console.log("plugin " + pluginVal.plugin + " not found");
        }
    }
}

gulp.task('copyFromJson', function() {
    copyFilter([{
        "plugin": "plugin_a_name",
        "types": ["js"]
    }, {
        "plugin": "plugin_b_name"
    }]);
});

gulp.task('default', ['copyFromJson']);