A way to initialize and launch an app or system.
In Angular, an app’s root NgModule (AppModule) has a bootstrap property that identifies the app’s top-level components.
例子：
import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { AppRoutingModule } from './app-routing.module';
import { AppComponent } from './app.component';
@NgModule({
declarations: [
AppComponent
],
imports: [
BrowserModule,
AppRoutingModule
],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule { } 其中bootstrap屬性的值AppComponent來自檔案app.component.ts：
During the bootstrap process,
Angularcreates and inserts these components into the index.html host web page.
index.html的内容：
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>MyFirstProject</title>
<base href="/">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="icon" type="image/x-icon" href="favicon.ico">
</head>
<body>
<app-root></app-root>
</body>
</html>
這個app-root的标簽：
定義在app.component.ts的Component selector裡: