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<html><script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.6.9/angular.min.js"></script> <style>textarea.ng-invalid { background-color:pink;}textarea.ng-valid { background-color:lightgreen;}</style><body ng-app=""><p>Try writing in the textarea field:</p><textarea ng-model="myName" required>The textarea requires content, and will therefore become green when you write in it.