<!-- #docplaster -->
<a id="toc"></a>
<h1>Template Syntax</h1>
<a href="#interpolation">Interpolation</a><br>
<a href="#expression-context">Expression context</a><br>
<a href="#statement-context">Statement context</a><br>
<a href="#mental-model">Mental Model</a><br>
<a href="#buttons">Buttons</a><br>
<a href="#prop-vs-attrib">Properties vs. Attributes</a><br>
<br>
<a href="#property-binding">Property Binding</a><br>
<div style="margin-left:8px">
  <a href="#attribute-binding">Attribute Binding</a><br>
  <a href="#class-binding">Class Binding</a><br>
  <a href="#style-binding">Style Binding</a><br>
</div>
<br>
<a href="#event-binding">Event Binding</a><br>
<a href="#two-way">Two-way Binding</a><br>
<br>
<div>Directives</div>
<div style="margin-left:8px">
  <a href="#ngModel">NgModel (two-way) Binding</a><br>
  <a href="#ngClass">NgClass Binding</a><br>
  <a href="#ngStyle">NgStyle Binding</a><br>
  <a href="#ngIf">NgIf</a><br>
  <a href="#ngFor">NgFor</a><br>
  <div style="margin-left:8px">
    <a href="#ngFor-index">NgFor with index</a><br>
    <a href="#ngFor-trackBy">NgFor with trackBy</a><br>
  </div>
  <a href="#ngSwitch">NgSwitch</a><br>
</div>
<br>
<a href="#ref-vars">Template reference variables</a><br>
<a href="#inputs-and-outputs">Inputs and outputs</a><br>
<a href="#pipes">Pipes</a><br>
<a href="#safe-navigation-operator">Safe navigation operator <i>?.</i></a><br>
<a href="#non-null-assertion-operator">Non-null assertion operator <i>!.</i></a><br>
<a href="#enums">Enums</a><br>
<a href="#svg-templates">SVG Templates</a><br>

<!-- Interpolation and expressions -->
<hr><h2 id="interpolation">Interpolation</h2>

<p>My current hero is {{currentHero.name}}</p>

<h3>
  {{title}}
  <img src="{{heroImageUrl}}" style="height:30px">
</h3>

<!-- "The sum of 1 + 1 is 2" -->
<p>The sum of 1 + 1 is {{1 + 1}}</p>

<!-- "The sum of 1 + 1 is not 4" -->
<p>The sum of 1 + 1 is not {{1 + 1 + getVal()}}</p>

<a class="to-toc" href="#toc">top</a>

<hr><h2 id="expression-context">Expression context</h2>

<p>Component expression context (&#123;&#123;title&#125;&#125;, [hidden]="isUnchanged")</p>
<div class="context">
  {{title}}
  <span [hidden]="isUnchanged">changed</span>
</div>


<p>Template input variable expression context (let hero)</p>
<!-- template hides the following; plenty of examples later -->
<ng-template>
  <div *ngFor="let hero of heroes">{{hero.name}}</div>
</ng-template>

<p>Template reference variable expression context (#heroInput)</p>
<div (keyup)="0" class="context">
  Type something:
  <input #heroInput> {{heroInput.value}}
</div>

<a class="to-toc" href="#toc">top</a>

<hr><h2 id="statement-context">Statement context</h2>

<p>Component statement context ( (click)="onSave() )
<div class="context">
  <!-- #docregion context-component-statement -->
  <button (click)="deleteHero()">Delete hero</button>
  <!-- #enddocregion context-component-statement -->
</div>

<p>Template $event statement context</p>
<div class="context">
  <!-- #docregion context-var-statement -->
  <button (click)="onSave($event)">Save</button>
  <!-- #enddocregion context-var-statement -->
</div>

<p>Template input variable statement context (let hero)</p>
<!-- template hides the following; plenty of examples later -->
<div class="context">
  <!-- #docregion context-var-statement -->
  <button *ngFor="let hero of heroes" (click)="deleteHero(hero)">{{hero.name}}</button>
  <!-- #enddocregion context-var-statement -->
</div>

<p>Template reference variable statement context (#heroForm)</p>
<div class="context">
  <!-- #docregion context-var-statement -->
  <form #heroForm (ngSubmit)="onSubmit(heroForm)"> ... </form>
  <!-- #enddocregion context-var-statement -->
</div>

<a class="to-toc" href="#toc">top</a>

<!-- New Mental Model -->
<hr><h2 id="mental-model">New Mental Model</h2>

<!--<img src="https://wpclipart.com/cartoon/people/hero/hero_silhoutte_T.png">-->
<!-- Public Domain terms of use: https://wpclipart.com/terms.html -->
<div class="special">Mental Model</div>
<img src="assets/images/hero.png">
<button disabled>Save</button>
<br><br>

<div>
  <!-- Normal HTML -->
  <div class="special">Mental Model</div>
  <!-- Wow! A new element! -->
  <app-hero-detail></app-hero-detail>
</div>
<br><br>

<div>
  <!-- Bind button disabled state to `isUnchanged` property -->
  <button [disabled]="isUnchanged">Save</button>
</div>
<br><br>

<div>
  <!-- #docregion property-binding-syntax-1 -->
  <img [src]="heroImageUrl">
  <app-hero-detail [hero]="currentHero"></app-hero-detail>
  <div [ngClass]="{'special': isSpecial}"></div>
  <!-- #enddocregion property-binding-syntax-1 -->
</div>
<br><br>

<!-- #docregion event-binding-syntax-1 -->
<button (click)="onSave()">Save</button>
<app-hero-detail (deleteRequest)="deleteHero()"></app-hero-detail>
<div (myClick)="clicked=$event" clickable>click me</div>
<!-- #enddocregion event-binding-syntax-1 -->
{{clicked}}
<br><br>

<div>
  Hero Name:
  <!-- #docregion 2-way-binding-syntax-1 -->
  <input [(ngModel)]="name">
  <!-- #enddocregion 2-way-binding-syntax-1 -->
  {{name}}
</div>
<br><br>

<!-- #docregion attribute-binding-syntax-1 -->
<button [attr.aria-label]="help">help</button>
<!-- #enddocregion attribute-binding-syntax-1 -->
<br><br>

<!-- #docregion class-binding-syntax-1 -->
<div [class.special]="isSpecial">Special</div>
<!-- #enddocregion class-binding-syntax-1 -->
<br><br>

<!-- #docregion style-binding-syntax-1 -->
<button [style.color]="isSpecial ? 'red' : 'green'">
<!-- #enddocregion style-binding-syntax-1 -->
button</button>

<a class="to-toc" href="#toc">top</a>

<!-- property vs. attribute -->
<hr><h2 id="prop-vs-attrib">Property vs. Attribute (img examples)</h2>
<!-- examine the following <img> tag in the browser tools -->
<img src="images/ng-logo.png"
    [src]="heroImageUrl">

<br><br>

<img [src]="iconUrl"/>
<img bind-src="heroImageUrl"/>
<img [attr.src]="villainImageUrl"/>

<a class="to-toc" href="#toc">top</a>

<!-- buttons -->
<hr><h2 id="buttons">Buttons</h2>

<button>Enabled (but does nothing)</button>
<button disabled>Disabled</button>
<button disabled=false>Still disabled</button>
<br><br>
<button disabled>disabled by attribute</button>
<button [disabled]="isUnchanged">disabled by property binding</button>
<br><br>
<button bind-disabled="isUnchanged" on-click="onSave($event)">Disabled Cancel</button>
<button [disabled]="!canSave" (click)="onSave($event)">Enabled Save</button>

<a class="to-toc" href="#toc">top</a>

<!-- property binding -->
<hr><h2 id="property-binding">Property Binding</h2>

<img [src]="heroImageUrl">
<button [disabled]="isUnchanged">Cancel is disabled</button>
<div [ngClass]="classes">[ngClass] binding to the classes property</div>
<app-hero-detail [hero]="currentHero"></app-hero-detail>
<img bind-src="heroImageUrl">

<!-- ERROR: HeroDetailComponent.hero expects a Hero object, not the string "currentHero" -->
<!-- <app-hero-detail hero="currentHero"></app-hero-detail> -->

<app-hero-detail prefix="You are my" [hero]="currentHero"></app-hero-detail>

<p><img src="{{heroImageUrl}}"> is the <i>interpolated</i> image.</p>
<p><img [src]="heroImageUrl"> is the <i>property bound</i> image.</p>

<p><span>"{{title}}" is the <i>interpolated</i> title.</span></p>
<p>"<span [innerHTML]="title"></span>" is the <i>property bound</i> title.</p>

<!--
  Angular generates warnings for these two lines as it sanitizes them
  WARNING: sanitizing HTML stripped some content (see https://g.co/ng/security#xss).
 -->
<p><span>"{{evilTitle}}" is the <i>interpolated</i> evil title.</span></p>
<p>"<span [innerHTML]="evilTitle"></span>" is the <i>property bound</i> evil title.</p>

<a class="to-toc" href="#toc">top</a>

<!-- attribute binding -->
<hr><h2 id="attribute-binding">Attribute Binding</h2>

<!--  create and set a colspan attribute -->
<table border=1>
  <!--  expression calculates colspan=2 -->
  <tr><td [attr.colspan]="1 + 1">One-Two</td></tr>

  <!-- ERROR: There is no `colspan` property to set!
    <tr><td colspan="{{1 + 1}}">Three-Four</td></tr>
  -->

  <tr><td>Five</td><td>Six</td></tr>
</table>

<br>
<!-- create and set an aria attribute for assistive technology -->
<button [attr.aria-label]="actionName">{{actionName}} with Aria</button>
<br><br>

<!-- The following effects are not discussed in the chapter -->
<div>
  <!-- any use of [attr.disabled] creates the disabled attribute -->
  <button [attr.disabled]="isUnchanged">Disabled</button>

  <button [attr.disabled]="!isUnchanged">Disabled as well</button>

  <!-- we'd have to remove it with property binding -->
  <button disabled [disabled]="false">Enabled (but inert)</button>
</div>

<a class="to-toc" href="#toc">top</a>

<!-- class binding -->
<hr><h2 id="class-binding">Class Binding</h2>

<!-- standard class attribute setting  -->
<div class="bad curly special">Bad curly special</div>

<!-- reset/override all class names with a binding  -->
<div class="bad curly special"
     [class]="badCurly">Bad curly</div>

<!-- toggle the "special" class on/off with a property -->
<div [class.special]="isSpecial">The class binding is special</div>

<!-- binding to `class.special` trumps the class attribute -->
<div class="special"
     [class.special]="!isSpecial">This one is not so special</div>

<div bind-class.special="isSpecial">This class binding is special too</div>

<a class="to-toc" href="#toc">top</a>

<!--style binding -->
<hr><h2 id="style-binding">Style Binding</h2>

<button [style.color]="isSpecial ? 'red': 'green'">Red</button>
<button [style.background-color]="canSave ? 'cyan': 'grey'" >Save</button>

<button [style.font-size.em]="isSpecial ? 3 : 1" >Big</button>
<button [style.font-size.%]="!isSpecial ? 150 : 50" >Small</button>

<a class="to-toc" href="#toc">top</a>

<!-- event binding -->
<hr><h2 id="event-binding">Event Binding</h2>

<button (click)="onSave()">Save</button>

<button on-click="onSave()">On Save</button>

<div>
<!-- `myClick` is an event on the custom `ClickDirective` -->
<div (myClick)="clickMessage=$event" clickable>click with myClick</div>
{{clickMessage}}
</div>


<!-- binding to a nested component -->
<app-hero-detail (deleteRequest)="deleteHero($event)" [hero]="currentHero"></app-hero-detail>
<br>

<app-big-hero-detail
    (deleteRequest)="deleteHero($event)"
    [hero]="currentHero">
</app-big-hero-detail>

<div class="parent-div" (click)="onClickMe($event)" clickable>Click me
  <div class="child-div">Click me too!</div>
</div>

<!-- Will save only once -->
<div (click)="onSave()" clickable>
  <button (click)="onSave($event)">Save, no propagation</button>
</div>

<!-- Will save twice -->
<div (click)="onSave()" clickable>
  <button (click)="onSave()">Save w/ propagation</button>
</div>

<a class="to-toc" href="#toc">top</a>

<hr><h2 id="two-way">Two-way Binding</h2>
<div id="two-way-1">
  <app-sizer [(size)]="fontSizePx"></app-sizer>
  <div [style.font-size.px]="fontSizePx">Resizable Text</div>
  <label>FontSize (px): <input [(ngModel)]="fontSizePx"></label>
</div>
<br>
<div id="two-way-2">
  <h3>De-sugared two-way binding</h3>
  <app-sizer [size]="fontSizePx" (sizeChange)="fontSizePx=$event"></app-sizer>
</div>

<a class="to-toc" href="#toc">top</a>

<!-- Two way data binding unwound;
    passing the changed display value to the event handler via `$event` -->
<hr><h2 id="ngModel">NgModel (two-way) Binding</h2>

<h3>Result: {{currentHero.name}}</h3>

<input [value]="currentHero.name"
       (input)="updateCurrentHeroName($event)">
without NgModel
<br>
<input [(ngModel)]="currentHero.name">
[(ngModel)]
<br>
<input bindon-ngModel="currentHero.name">
bindon-ngModel
<br>
<input
  [ngModel]="currentHero.name"
  (ngModelChange)="currentHero.name=$event">
(ngModelChange)="...name=$event"
<br>
<input
  [ngModel]="currentHero.name"
  (ngModelChange)="setUppercaseName($event)">
(ngModelChange)="setUppercaseName($event)"

<a class="to-toc" href="#toc">top</a>

<!-- NgClass binding -->
<hr><h2 id="ngClass">NgClass Binding</h2>

<p>currentClasses is {{currentClasses | json}}</p>
<div [ngClass]="currentClasses">This div is initially saveable, unchanged, and special</div>

<!-- not used in chapter -->
<br>
<label>saveable   <input type="checkbox" [(ngModel)]="canSave"></label> |
<label>modified:  <input type="checkbox" [value]="!isUnchanged" (change)="isUnchanged=!isUnchanged"></label> |
<label>special:   <input type="checkbox" [(ngModel)]="isSpecial"></label>
<button (click)="setCurrentClasses()">Refresh currentClasses</button>
<br><br>
<div [ngClass]="currentClasses">
  This div should be {{ canSave ? "": "not"}} saveable,
                  {{ isUnchanged ? "unchanged" : "modified" }} and,
                  {{ isSpecial ? "": "not"}} special after clicking "Refresh".</div>
<br><br>

<div [ngClass]="isSpecial ? 'special' : ''">This div is special</div>

<div class="bad curly special">Bad curly special</div>
<div [ngClass]="{'bad':false, 'curly':true, 'special':true}">Curly special</div>

<a class="to-toc" href="#toc">top</a>

<!-- NgStyle binding -->
<hr><h2 id="ngStyle">NgStyle Binding</h2>

<div [style.font-size]="isSpecial ? 'x-large' : 'smaller'" >
  This div is x-large or smaller.
</div>

<h3>[ngStyle] binding to currentStyles - CSS property names</h3>
<p>currentStyles is {{currentStyles | json}}</p>
<div [ngStyle]="currentStyles">
  This div is initially italic, normal weight, and extra large (24px).
</div>

<!-- not used in chapter -->
<br>
<label>italic: <input type="checkbox" [(ngModel)]="canSave"></label> |
<label>normal: <input type="checkbox" [(ngModel)]="isUnchanged"></label> |
<label>xlarge: <input type="checkbox" [(ngModel)]="isSpecial"></label>
<button (click)="setCurrentStyles()">Refresh currentStyles</button>
<br><br>
<div [ngStyle]="currentStyles">
  This div should be {{ canSave ? "italic": "plain"}},
                  {{ isUnchanged ? "normal weight" : "bold" }} and,
                  {{ isSpecial ? "extra large": "normal size"}} after clicking "Refresh".</div>

<a class="to-toc" href="#toc">top</a>

<!-- NgIf binding -->
<hr><h2 id="ngIf">NgIf Binding</h2>

<app-hero-detail *ngIf="isActive"></app-hero-detail>

<div *ngIf="currentHero">Hello, {{currentHero.name}}</div>
<div *ngIf="nullHero">Hello, {{nullHero.name}}</div>

<!-- NgIf binding with template (no *) -->

<ng-template [ngIf]="currentHero">Add {{currentHero.name}} with template</ng-template>

<!-- Does not show because isActive is false! -->
<div>Hero Detail removed from DOM (via template) because isActive is false</div>
<ng-template [ngIf]="isActive">
  <app-hero-detail></app-hero-detail>
</ng-template>

<!-- isSpecial is true -->
<div [class.hidden]="!isSpecial">Show with class</div>
<div [class.hidden]="isSpecial">Hide with class</div>

<!-- HeroDetail is in the DOM but hidden -->
<app-hero-detail [class.hidden]="isSpecial"></app-hero-detail>

<div [style.display]="isSpecial ? 'block' : 'none'">Show with style</div>
<div [style.display]="isSpecial ? 'none'  : 'block'">Hide with style</div>

<a class="to-toc" href="#toc">top</a>

<!-- NgFor binding -->
<hr><h2 id="ngFor">NgFor Binding</h2>

<div class="box">
  <div *ngFor="let hero of heroes">{{hero.name}}</div>
</div>
<br>

<div class="box">
  <!-- *ngFor w/ hero-detail Component -->
  <app-hero-detail *ngFor="let hero of heroes" [hero]="hero"></app-hero-detail>
</div>

<a class="to-toc" href="#toc">top</a>

<h4 id="ngFor-index">*ngFor with index</h4>
<p>with <i>semi-colon</i> separator</p>
<div class="box">
  <div *ngFor="let hero of heroes; let i=index">{{i + 1}} - {{hero.name}}</div>
</div>

<p>with <i>comma</i> separator</p>
<div class="box">
  <!-- Ex: "1 - Hercules" -->
  <div *ngFor="let hero of heroes, let i=index">{{i + 1}} - {{hero.name}}</div>
</div>

<a class="to-toc" href="#toc">top</a>

<h4 id="ngFor-trackBy">*ngFor trackBy</h4>
<button (click)="resetHeroes()">Reset heroes</button>
<button (click)="changeIds()">Change ids</button>
<button (click)="clearTrackByCounts()">Clear counts</button>

<p><i>without</i> trackBy</p>
<div class="box">
  <div #noTrackBy *ngFor="let hero of heroes">({{hero.id}}) {{hero.name}}</div>

  <div id="noTrackByCnt" *ngIf="heroesNoTrackByCount" >
    Hero DOM elements change #{{heroesNoTrackByCount}} without trackBy
  </div>
</div>

<p>with trackBy</p>
<div class="box">
  <div #withTrackBy *ngFor="let hero of heroes; trackBy: trackByHeroes">({{hero.id}}) {{hero.name}}</div>

  <div id="withTrackByCnt" *ngIf="heroesWithTrackByCount">
    Hero DOM elements change #{{heroesWithTrackByCount}} with trackBy
  </div>
</div>

<br><br><br>

<p>with trackBy and <i>semi-colon</i> separator</p>
<div class="box">
  <div *ngFor="let hero of heroes; trackBy: trackByHeroes">
    ({{hero.id}}) {{hero.name}}
  </div>
</div>

<p>with trackBy and <i>comma</i> separator</p>
<div class="box">
  <div *ngFor="let hero of heroes, trackBy: trackByHeroes">({{hero.id}}) {{hero.name}}</div>
</div>

<p>with trackBy and <i>space</i> separator</p>
<div class="box">
  <div *ngFor="let hero of heroes trackBy: trackByHeroes">({{hero.id}}) {{hero.name}}</div>
</div>

<p>with <i>generic</i> trackById function</p>
<div class="box">
  <div *ngFor="let hero of heroes, trackBy: trackById">({{hero.id}}) {{hero.name}}</div>
</div>

<a class="to-toc" href="#toc">top</a>

<!-- NgSwitch binding -->
<hr><h2 id="ngSwitch">NgSwitch Binding</h2>

<p>Pick your favorite hero</p>
<div>
  <label *ngFor="let h of heroes">
    <input type="radio" name="heroes" [(ngModel)]="currentHero" [value]="h">{{h.name}}
  </label>
</div>

<div [ngSwitch]="currentHero.emotion">
  <app-happy-hero    *ngSwitchCase="'happy'"    [hero]="currentHero"></app-happy-hero>
  <app-sad-hero      *ngSwitchCase="'sad'"      [hero]="currentHero"></app-sad-hero>
  <app-confused-hero *ngSwitchCase="'confused'" [hero]="currentHero"></app-confused-hero>
  <div *ngSwitchCase="'confused'">Are you as confused as {{currentHero.name}}?</div>
  <app-unknown-hero  *ngSwitchDefault           [hero]="currentHero"></app-unknown-hero>
</div>

<a class="to-toc" href="#toc">top</a>

<!-- template reference variable -->
<hr><h2 id="ref-vars">Template reference variables</h2>

<input #phone placeholder="phone number">

<!-- lots of other elements -->

<!-- phone refers to the input element; pass its `value` to an event handler -->
<button (click)="callPhone(phone.value)">Call</button>

<input ref-fax placeholder="fax number">
<button (click)="callFax(fax.value)">Fax</button>

<!-- btn refers to the button element; show its disabled state -->
<button #btn disabled [innerHTML]="'disabled by attribute: '+btn.disabled"></button>

<h4>Example Form</h4>
<app-hero-form [hero]="currentHero"></app-hero-form>

<a class="to-toc" href="#toc">top</a>

<!-- inputs and output -->
<hr><h2 id="inputs-and-outputs">Inputs and Outputs</h2>

<img [src]="iconUrl"/>
<button (click)="onSave()">Save</button>

<app-hero-detail [hero]="currentHero" (deleteRequest)="deleteHero($event)">
</app-hero-detail>

<div (myClick)="clickMessage2=$event" clickable>myClick2</div>
{{clickMessage2}}

<a class="to-toc" href="#toc">top</a>

<!-- Pipes -->
<hr><h2 id="pipes">Pipes</h2>

<div>Title through uppercase pipe: {{title | uppercase}}</div>

<!-- Pipe chaining: convert title to uppercase, then to lowercase -->
<div>
  Title through a pipe chain:
  {{title | uppercase | lowercase}}
</div>

<!-- pipe with configuration argument => "February 25, 1970" -->
<div>Birthdate: {{currentHero?.birthdate | date:'longDate'}}</div>

<div>{{currentHero | json}}</div>

<div>Birthdate: {{(currentHero?.birthdate | date:'longDate') | uppercase}}</div>

<div>
  <!-- pipe price to USD and display the $ symbol -->
  <label>Price: </label>{{product.price | currency:'USD':'symbol'}}
</div>

<a class="to-toc" href="#toc">top</a>

<!-- Null values and the safe navigation operator -->
<hr><h2 id="safe-navigation-operator">Safe navigation operator <i>?.</i></h2>

<div>
  The title is {{title}}
</div>

<div>
  The current hero's name is {{currentHero?.name}}
</div>

<div>
  The current hero's name is {{currentHero.name}}
</div>


<!--
The null hero's name is {{nullHero.name}}

See console log:
  TypeError: Cannot read property 'name' of null in [null]
-->

<!--No hero, div not displayed, no error -->
<div *ngIf="nullHero">The null hero's name is {{nullHero.name}}</div>

<div>
The null hero's name is {{nullHero && nullHero.name}}
</div>

<div>
  <!-- No hero, no problem! -->
  The null hero's name is {{nullHero?.name}}
</div>


<a class="to-toc" href="#toc">top</a>

<!-- non-null assertion operator -->
<hr><h2 id="non-null-assertion-operator">Non-null assertion operator <i>!.</i></h2>

<div>
  <!--No hero, no text -->
  <div *ngIf="hero">
    The hero's name is {{hero!.name}}
  </div>
</div>

<a class="to-toc" href="#toc">top</a>

<!-- non-null assertion operator -->
<hr><h2 id="any-type-cast-function">$any type cast function <i>$any( )</i>.</h2>

<div>
  <!-- Accessing an undeclared member -->
  <div>
    The hero's marker is {{$any(hero).marker}}
  </div>
</div>

<div>
  <!-- Accessing an undeclared member -->
  <div>
    Undeclared members is {{$any(this).member}}
  </div>
</div>

<a class="to-toc" href="#toc">top</a>

<!-- TODO: discuss this in the Style binding section -->
<!-- enums in bindings -->
<hr><h2 id="enums">Enums in binding</h2>

<p>
  The name of the Color.Red enum is {{Color[Color.Red]}}.<br>
  The current color is {{Color[color]}} and its number is {{color}}.<br>
  <button [style.color]="Color[color]" (click)="colorToggle()">Enum Toggle</button>
</p>

<a class="to-toc" href="#toc">top</a>

<hr><h2 id="svg-templates">SVG Templates</h2>
<app-svg></app-svg>
<a class="to-toc" href="#toc">top</a>
