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JSON-stringify-Object.html - JSON.stringify() on Objects

Q

How JSON.stringify() behaves on JavaScript objects?

✍: FYIcenter.com

A

When processing an object, JSON.stringify() behave depending on the type of objects based on the following rules:

Boolean, Number, and String objects are converted to the corresponding primitive JSON values during stringification.
Date objects are converted JSON strings according the ISO standard.
All other objects are converted JSON objects with their enumerable properties only.
Functions are removed if inside an object, or converted to "null" if inside an array, or converted to "undefined" if by itself.
"undefined" are removed if inside an object, or converted to "null" if inside an array, or converted to "undefined" if by itself.

Here is a JavaScript example showing how different types of objects get stringified:

<!-- JSON-stringify-Object.html
     Copyright (c) FYIcenter.com 
-->
<html>
<body>
<script type="text/javascript">

function myFunc() {
   return "Hello!";
}
   
   var myObj = new Object();
   myObj.name = "Joe";
   Object.defineProperty(myObj, 'age', {value: 1, enumerable: false});
   Object.defineProperty(myObj, 'type', {value: 'User', enumerable: true});

   var str = null;
   
   document.write("<p>String from JSON.stringify():</p>");
   document.write("<pre>");

   str = JSON.stringify(new String("false"));
   document.write("   String object = "+str+"\n");

   str = JSON.stringify(new Boolean(false));
   document.write("   Boolean object = "+str+"\n");

   str = JSON.stringify(new Date(2006, 0, 2, 15, 4, 5));
   document.write("   Date object = "+str+"\n");

   str = JSON.stringify(myObj);
   document.write("   Object object = "+str+"\n");

   str = JSON.stringify(JSON);
   document.write("   JSON object = "+str+"\n");

   str = JSON.stringify(myFunc);
   document.write("   Function object = "+str+"\n");

   document.write("</pre>");
</script>
</body>
</html>

Save the above code in a file, JSON-stringify-Object.html, and open it in a Web browser. You see the following output:

String from JSON.stringify():

   String object = "false"
   Boolean object = false
   Date object = "2006-01-02T20:04:05.000Z"
   Object object = {"name":"Joe","type":"User"}
   JSON object = {}
   Function object = undefined

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2017-09-08, 1240👍, 0💬