RxJS 5.5 has undergone a significant change and has introduced lettable operators to replace the traditional operators we were using previously.
In the article, there is a note that states:
Lettable operators can now be imported from rxjs/operators, but doing so without changing your build process can result in a larger application bundle. This is because rxjs/operators will resolve to the CommonJS output of rxjs by default.
This statement can be validated easily with a new AngularCLI-generated app.
For instance, when we have an application that doesn't import anything from RxJS:
import { Component, OnInit } from '@angular/core';
import { HttpClient } from "@angular/common/http";
@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {
public title = 'app';
constructor(private readonly http: HttpClient) {
}
public ngOnInit(): void {
this.http.get('https://api.github.com/users')
.subscribe(response => {
console.log(response);
});
}
}
Upon building the application using ng build --prod, the bundle sizes remain the same.
However, when we import a traditional RxJS operator and use it:
import { Component, OnInit } from '@angular/core';
import { HttpClient } from "@angular/common/http";
import "rxjs/add/operator/map";
@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {
public title = 'app';
constructor(private readonly http: HttpClient) {
}
public ngOnInit(): void {
this.http.get('https://api.github.com/users')
.map((u: any) => 1)
.subscribe(response => {
console.log(response);
});
}
}
There is still no difference in the bundle sizes.
On the other hand, when we try to import and use the lettable operator as recommended without modifying the build process:
import { Component, OnInit } from '@angular/core';
import { HttpClient } from "@angular/common/http";
import { map } from "rxjs/operators";
@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {
public title = 'app';
constructor(private readonly http: HttpClient) {
}
public ngOnInit(): void {
this.http.get('https://api.github.com/users').pipe(
map((u: any) => 1))
.subscribe(response => {
console.log(response);
});
}
}
In this case, the vendor bundle size increases, indicating that RxJS hasn't been tree-shaked:
chunk {0} polyfills.e1f97a0070e18e96a6be.bundle.js (polyfills) 61.4 kB {4} [initial] [rendered]
chunk {1} main.450c741a106157402dcd.bundle.js (main) 4.97 kB {3} [initial] [rendered]
chunk {2} styles.d41d8cd98f00b204e980.bundle.css (styles) 0 bytes {4} [initial] [rendered]
chunk {3} vendor.3f53f0e2283f4c44ec38.bundle.js (vendor) 344 kB [initial] [rendered]
chunk {4} inline.2d973ef5a10aa806b082.bundle.js (inline) 1.45 kB [entry] [rendered]
Attempting to import the lettable operator as recommended in the article results in a build error:
./src/app/app.component.ts
Module not found: Error: Can't resolve 'rxjs/operators/map' in 'c:\Projects\Angular\src\app'
@ ./src/app/app.component.ts 14:0-41
@ ./src/app/app.module.ts
@ ./src/main.ts
@ multi webpack-dev-server/client?http://localhost:4200 ./src/main.ts
- What could be the issue here?
- How can we import the new RxJS lettable operators in an Angular CLI app while ensuring that RxJS is still tree-shaked?
UPDATE: Package versions are as follows:
rxjs: 5.5.0
@angular/cli: 1.4.9
node: 8.6.0
os: win32 x64
@angular/animations: 4.4.6
@angular/common: 4.4.6
@angular/compiler: 4.4.6
@angular/core: 4.4.6
@angular/forms: 4.4.6
@angular/http: 4.4.6
@angular/platform-browser: 4.4.6
@angular/platform-browser-dynamic: 4.4.6
@angular/router: 4.4.6
@angular/cli: 1.4.9
@angular/compiler-cli: 4.4.6
@angular/language-service: 4.4.6
typescript: 2.3.4