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Angular Templates: Attribute Binding with attr.

Bind to HTML attributes with [attr.name] when no DOM property exists.

What is Attribute Binding with attr.?

• Use [attr.name] to set HTML attributes.
• For attributes that do not map to DOM properties (e.g., ARIA, colspan).
• Distinct from property binding.

When to use Attribute Binding

• When no corresponding DOM property exists.
• Use property binding for normal element properties.
• Common with ARIA attributes and table attr like colspan.

<button [attr.aria-label]="label">Click</button>

Code explained

• [attr.aria-label]: Sets the HTML aria-label attribute using the component value.
• attr.: Prefer attr. when there is no matching DOM property (e.g., ARIA, colspan).
• Property vs attribute: For normal element properties, use property binding (e.g., [disabled]), not attr..

Example

Bind to attributes using attr.:

import { bootstrapApplication } from '@angular/platform-browser';
import { Component } from '@angular/core';
@Component({
 selector: 'app-root',
 standalone: true,
 template: `
 <h3>Attribute binding (attr.)</h3>
 <button [attr.aria-label]="label" (click)="toggle()">Toggle label</button>
 <table border="1" style="margin-top:8px">
 <tr><th>A</th><th>B</th><th>C</th></tr>
 <tr><td [attr.colspan]="wide ? 2 : 1">Row 1</td><td>Cell</td><td>Cell</td></tr>
 </table>
 `
})
export class App {
 wide = true;
 get label() { return this.wide ? 'Table is wide' : 'Table is narrow'; }
 toggle() { this.wide = !this.wide; }
}
bootstrapApplication(App);

<app-root></app-root>

Example explained

• [attr.aria-label]="label": Binds the aria-label HTML attribute to the string returned by the component's label getter.
• [attr.colspan]="wide ? 2 : 1": Sets the table cell's colspan attribute based on state. Use attr. because colspan is an attribute, not a plain DOM property.
• get label(): Computes a descriptive string from the current wide value.
• toggle(): Flips wide to update both the label and the cell span.

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