javascript - Dependency Injection and Interfaces in Node -

coming c# background, used interfaces base mock objects off of. created custom mock objects myself , created mock implementation off c# interface.

how do in js or node? create interface can "mock" off of , interface serve real class able implement interface? make sense in js or or node world?

for example in java, same deal, define interface method stubs , use basis create real class or mock class off of.

unfortunately you're not going find standard interface part of javascript. i've never used c#, i've used java, , correct me if i'm wrong, looks you're talking creating interfaces , overriding methods both mock testing purposes, being able implement interfaces in other classes.

because isn't standard javascript feature, i think you'll find there going lot of broad answers here. however, idea of how popular libraries implement this, might suggest looking @ how angularjs looks @ mock testing (there many resources online, google it. starting point, @ how use ngmock module karma , jasmine.)

also, because of javascript's flexible nature, you'll find can override sort of "class method" (that is, function object member of object, whether new'ed "class" or plain object) re-implementing wherever need to... there's no special syntax it. understand , how accomplish this, i'd suggest looking ground @ how javascript using prototypal/prototypical inheritance. starting point might considering example this:

function cat(config) {   if(typeof config !== 'undefined') {     this.meow = config.meow; // config can possibly implement mock methods   } }  cat.prototype = {   this.meow = function() {     // meow want use part of "production" code   }; };  var config = {};  config.meow = function() {   // mock "meow" stuff };  var testcat = new cat(config); // 1 use mock "cat#meow"  var realcat = new cat(); // 1 use prototype "cat#meow" 

in above example, because of how javascript looks prototype chain, if sees implementation in class itself, it'll stop there , use method (thus, you've "overridden" prototype method). however, in example, if don't pass in config, it'll way prototype cat#meow method, , use one.

tl;dr: there's not 1 way implement javascript interfaces, ones double mocks (there's not best way implement dependency injection... that's foreign concept javascript itself, though many libraries implement cetain use-cases.)