Typically, you wouldn't need to do this dynamically as you would have specific $scope
properties on inputs
etc.
Here is an updated plunker.
HTML:
<div class="test" ng-controller="Ctrl">
<button ng-click="update(1, 'text1');">update text 1</button>
<button ng-click="update(2, 'text2');">update text 2</button>
{{text1}} , {{text2}}
<div>
JS:
function Ctrl($scope) {
$scope.update = function(parameter1, textVar){
if (parameter1 === 1) {$scope[textVar] = "1"}
if (parameter1 === 2) {$scope[textVar] = "2"}
};
}