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As I understand then combine multiple export statement into a single file is considered a good practice iff source file comes under the same directory

so 

import { Observable } from 'rxjs/Observable';
import { Observable, BehaviorSubject, Subject, ReplaySubject } from 'rxjs';

can be re-written to

import { Observable, BehaviorSubject, Subject, ReplaySubject } from 'rxjs';

But what If I have to import only one module than which is preferred way? using a complete file or a specific one.

import { Observable } from 'rxjs/Observable';

OR

import { Observable } from 'rxjs';

does that cost anything extra?

ts v 2.3.4

angular v 4.4.6

xkeshav
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1 Answers1

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import { Observable } from 'rxjs/Observable';

This is the efficient way to import a single module, because you are providing the exact path to only fetch the required module.

Whereas in this case,

import { Observable } from 'rxjs';

It will import a lot of unnecessary stuff from the rxjs library that will increase the page load time and/or the code base.

Sagar Chaudhary
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  • Thanks. so instead of `import { Observable, BehaviorSubject, Subject, ReplaySubject } from 'rxjs';` we have to include separate modules statement is also preferred? – xkeshav Oct 03 '18 at 07:40
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    Yeah, thats correct. Just to save time and code ,we import all in a single statement. – Sagar Chaudhary Oct 03 '18 at 07:56
  • your solution in not valid for rxjs5 , t is mentioned [here](https://github.com/ReactiveX/rxjs/blob/master/CHANGELOG.md) > deep imports: Can no longer deep import top-level types such as rxjs/Observable, rxjs/Subject, rxjs/ReplaySubject, et al. All imports should be done directly from rxjs, for example: import { Observable, Subject } from 'rxjs'; – xkeshav Oct 29 '18 at 04:38