Javascript 角度表达式 {{::}} 中的两个冒号是什么意思？
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What does two colons inside an angular expression {{::}} mean?
提问by J0B
What is the difference between:
有什么区别：
{{::office.name}}
and
和
{{office.name}}
in angularJS?
在 angularJS 中？
采纳答案by Teo.sk
回答by Tushar
One-time bindingFrom Angular Docs.
来自 Angular Docs的一次性绑定。
An expression that starts with
::is considered a one-time expression. One-time expressions will stop recalculating once they are stable, which happens after the first digest if the expression result is a non-undefined value (see value stabilization algorithm below).
以 开头的表达式
::被视为一次性表达式。一次性表达式一旦稳定就会停止重新计算，如果表达式结果是一个非未定义的值（参见下面的值稳定算法），这会在第一次摘要之后发生。
In many situations, the values need to be only shown in the view and are never going to update from view or controller. However, if two-way binding is used, $digestwill check for any changes in the expression in each cycle, which is not necessary. In these cases, ::should be used before expression. As stated in the above statement, this is more efficient than two-way binding syntax for such cases.
在许多情况下，这些值只需要显示在视图中，并且永远不会从视图或控制器中更新。但是，如果使用双向绑定，$digest将检查每个循环中表达式的任何变化，这是没有必要的。在这些情况下，::应该在表达式之前使用。如上述语句所述，在这种情况下，这比双向绑定语法更有效。
Blog: AngularJS one-time binding syntaxfrom @Todd Motto
博客：来自@Todd Motto 的AngularJS 一次性绑定语法
In a nut shell, when we declare a value such as
{{ ::foo }}inside the DOM, once this value becomes defined, Angular will render it, unbind it from the watchers and thus reduce the volume of bindings inside the$digestloop. Simple!
简而言之，当我们
{{ ::foo }}在 DOM 内部声明一个值时，一旦该值被定义，Angular 就会渲染它，将它与观察者解除绑定，从而减少$digest循环内的绑定量。简单的！
