​x
 
<!DOCTYPE html>
<html>
<script src="https://cdn.staticfile.net/angular.js/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>请试着在文本区域字段中输入：</p>
​
<textarea ng-model="myName" required></textarea>
​
</body>
</html>
​