- directive in module ng
The ngIf
directive removes or recreates a portion of the DOM tree based on an {expression}. If the expression assigned to ngIf
evaluates to a false value then the element is removed from the DOM, otherwise a clone of the element is reinserted into the DOM.
ngIf
differs from ngShow
and ngHide
in that ngIf
completely removes and recreates the element in the DOM rather than changing its visibility via the display
css property. A common case when this difference is significant is when using css selectors that rely on an element's position within the DOM, such as the :first-child
or :last-child
pseudo-classes.
Note that when an element is removed using ngIf
its scope is destroyed and a new scope is created when the element is restored. The scope created within ngIf
inherits from its parent scope using prototypal inheritance. An important implication of this is if ngModel
is used within ngIf
to bind to a javascript primitive defined in the parent scope. In this case any modifications made to the variable within the child scope will override (hide) the value in the parent scope.
Also, ngIf
recreates elements using their compiled state. An example of this behavior is if an element's class attribute is directly modified after it's compiled, using something like jQuery's .addClass()
method, and the element is later removed. When ngIf
recreates the element the added class will be lost because the original compiled state is used to regenerate the element.
Additionally, you can provide animations via the ngAnimate
module to animate the enter
and leave
effects.
Directive Info
- This directive creates new scope.
- This directive executes at priority level 600.
- This directive can be used as multiElement
Usage
- as attribute:
<ANY ng-if="expression"> ... </ANY>
Animations
Animation | Occurs |
---|---|
enter | just after the ngIf contents change and a new DOM element is created and injected into the ngIf container |
leave | just before the ngIf contents are removed from the DOM |
Arguments
Param | Type | Details |
---|---|---|
ngIf | expression | If the expression is falsy then the element is removed from the DOM tree. If it is truthy a copy of the compiled element is added to the DOM tree. |
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