Builtin-directive.md

Built-in Directives

• Directives are classes that add additional behavior to element.

• we can use built-in directives to manage forms, lists, styles ...

• Components: Used with a template. most common directive type. (ngModel, ngClass ...)

• Attribute directives: Change appearence or behavior...

• Structural directives: change the DOM layout by adding and removing DOM elements.

Built-in attribute directives

• Many NgModules such as RouterModule and the FormModule define their own attribute directive

• NgClass: Adds and removes a set of CSS classes.

• NgStyle: adds and removes a set of HTML styles.

• NgModel: Adds two-way data binding to an HTML form elementç

currentClasses: Record<string, boolean> = {};
/* . . . */
setCurrentClasses() {
  // CSS classes: added/removed per current state of component properties
  this.currentClasses =  {
    saveable: this.canSave,
    modified: !this.isUnchanged,
    special:  this.isSpecial
  };
}