how to select the value of a select dropdown using javascript/angularJS

this is how i am trying to access the select dropdown and now i want to select the option of which i have a value :

var A    
A= document.getElementById("aID");

this is the value i am getting while editing a row record using angular JS :

$scope.Act[index].ATextValue;

and i am trying to get which is wrong but i want the correct solution or way to do this :

 document.getElementById("aID").selectedValue=$scope.Act[index].ATextValue;

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Source Url how to select the value of a select dropdown using javascript/angularJS