JSforce has several features including Salesforce Metadata API access.
I previously wrote how JSforce can be used in Salesforce package deployment on Gulp.js, and there are NPM packages called gulp-jsforce-deploy or grunt-jsforce-deploy.
JSforce is useful not only for developing Salesforce application but also for learning Salesforce API itself.
JSforce has a "REPL mode" - you can issue an API request and confirm the result interactively from your terminal console.
You know there is a well-known web application to check Salesforce APIs casually - Workbench.
This web app does provide interfaces for many APIs of Salesforce, but just for checking the response.
It is not connected to the execution of scripts.
JSforce version 1.5 has been released which includes several important updates.
The release of 1.5 had been planned to be just after the release of Summer '15, but delayed almost 2 months
because I couldn't share the time to check all issues related to the release.
Sorry for the delay to everyone who longly anticipated.
The table of release contents is here,
but I'd like to pick up some features which become available in 1.5.
If you are developing an app on Lightning framework of Salesforce, you may know that the framework has
$A.enqueueAction() method call to invoke server-side Apex.
As the name suggests, it does not send the request to the server immediately -
it queues the request instead and bundle all requests queued during certain time period.
This mechanism is called "Boxcarred Action" - the salesforce.com evangelist Peter Chittum's blog.
In order to query the data stored in Salesforce, a query language named SOQL is used generally.
As Salesforce opens REST/SOAP API endpoint access, we can send the SOQL message in the API request.
This API can also be used when you are developing HTML5, Single Page Application(SPA).
You might have to care about Same Origin Policy and Cross Origin Resource Sharing (CORS) setting if the app resides outside of Salesforce,
but not applied to the case when the app is served on Visualforce Page.