Requirement description: There is a myimg variable in the page. I can use $scope.myimg='xxx' in the controller to give it an initial value. But if assignment is not allowed in the control, what about in the img tag? Give it an initial value?
<img ng-src='./img/{{myimg}}.png'>
This is the same operation as adding a default value when initializing a value in JavaScript, just use
||
.