How to check properties exits.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // type of operator/
        // example
        function Mobile(model_no){
            this.model = model_no;
        }
        var samsung = new Mobile('Galaxy');
        var nokia = new Mobile ('3300');
        if(typeof nokia. memory !== 'undefined'){
            document.write("available");
        }
        else{
            document.write("Doestn't exits");
        }

        // in Operator
        function Mobile(model_no){
            this.model = model_no;
            this.memory = model_no;
            this.memory = 4;
        }
        var samsung = new Mobile('Galaxy');
        var nokia = new Mobile ('3300');
        if('memory' in nokia ){
            document.write("available");
        }
        else{
            document.write("Doestn't exits");
        }

        // hasOwnProperty()
        function Mobile(model_no){
            this.model = model_no;
            this.coloe = 'white';

        }
        var samsung = new Mobile('Galaxy');
        var nokia = new Mobile ('3300');
        if(nokia.hasOwnProperty('color')){
            document.write("available");
        }
        else{
            document.write("Doestn't exits");
        }
    </script>
</body>
</html>