angular.js - angularjs {{}}questions

Question

Why does {{a}} output

in the html interface?

html<span class="ng-binding ng-scope">
4
</span>

And what I expected was

html4

Have you ever encountered a master who can help you with your questions~

Answer 1

Quoted from the official website:

The ngBind attribute tells Angular to replace the text content of the
specified HTML element with the value of a given expression, and to
update the text content when the value of that expression changes.

means just ngBind会告诉angular去将你写的表达式替换成一个特殊的html元素.

And this 特殊的html元素 is the span with class,

Double curly brackets{{}}和ngBind是一样的，实际上是一个directive, there is only a slight difference in the scope of application

Official Document ngBind

Answer 2

The HTML value output by AngularJs ng-bind will definitely not be just 4. Otherwise, how to control the position of the output value?

Answer 3

aHow is the value of this variable assigned?
Generally $scope.a=4;
The output result of {{a}} is 4.

Answer 4

Thanks for the invitation. You can see it in the source code of angular https://github.com/angular/angular.js/blob/master/src/ng/compile.js#L1...
In fact, it is used to bind data to this "top text node"