How to use System.import() correctly? - node.js

Question

I use the jspm in my project.
But I need the server side nodejs file to execute some instruction.
For example, I need to use the lodash and found the guide in the https://github.com/systemjs/systemjs
var System = require('jspm').Loader();
System.import('lodash').then(function (_) { console.log(_); });
However, I want to use the lodash globally.
Just like
var _ = System.import('lodash');
var myArr = _.map([1, 2, 3], function(n) { return n * 3; });
It will show
TypeError: _.map is not a function
at Object. (/Users/joyfeel/javascript/jspm-test/index.js:49:16)
at Module._compile (module.js:435:26)
at normalLoader (/usr/local/lib/node_modules/babel/node_modules/babel-core/lib/api/register/node.js:199:5)
at Object.require.extensions.(anonymous function) [as .js] (/usr/local/lib/node_modules/babel/node_modules/babel-core/lib/api/register/node.js:216:7)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:311:12)
at Function.Module.runMain (module.js:467:10)
at Object. (/usr/local/lib/node_modules/babel/lib/_babel-node.js:144:25)
at Module._compile (module.js:435:26)
at Object.Module._extensions..js (module.js:442:10)
Why does the lodash only be used in .then scope?
Could anyone tell me how to figure it out? Suppose we want to System.import other modules and use it?

Answer 1

_ can only be accessed in the scope of then because System.import always returns a Promise.
Therefore you have to wait for the Promise to be resolved before you can access its result.
Anyway i would not recommend you to use lodash globally.
But when you really want to use _ globally you can do something like:
System.import('lodash').then(function(_) {
GLOBAL._ = _;
});
Still you have to make sure that all code that uses GLOBAL._ waits till the Promise from the lodash import is resolved.
But again: i would discourage you doing it that way but recommend that you import lodash in every module that needs it.