Angular lazy one-time binding for expressions

javascript angularjs binding lazy-evaluation
seldary picture seldary · May 31, 2014 · Viewed 20.1k times · Source

AngularJS has a new feature since the version 1.3.0-beta.10: the "lazy one-time binding".

Simple expressions can be prefixed with ::, telling angular to stop watching after the expression was first evaluated. The common example given is something like:

<div>{{::user.name}}</div>

Is there a similar syntax for expressions like the following ones?

<div ng-if="user.isSomething && user.isSomethingElse"></div>
<div ng-class="{classNameFoo: user.isSomething}"></div>

Answer

Blackhole picture Blackhole · May 31, 2014

Yes. You can prefix every expressions with ::, even the ones in ngIf or ngClass:

<div ng-if="::(user.isSomething && user.isSomethingElse)"></div>
<div ng-class="::{classNameFoo: user.isSomething}"></div>

Actually, the code simply checks that the two first characters in the expression are : in order to activate the one-time binding (and then removes them, thus the parenthesis aren't even needed). Everything else remains the same.

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