How to write a replacer array to filter values while the JSON.stringify() function is generating the JSON text string?

If you call JSON.stringify() with an array as the replacer, the array elements will be used to filters to select object properties with keys match one of array elements. All other object properties will be dropped. But all array elements and standalone values will be remain in the output.

Here is a JavaScript example that a replacer array to keep only "name" and "group" properties in any objects, and filter out all other properties. But array elements are staying in the output.

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

   var filter = ["name", "group"];

function stringifier(val) {
   var str = JSON.stringify(val, ["name", "group"]);
   return str;
}

   document.write("<p>JSON.stringify() Replacer to Transform Values:</p>");
   document.write("<pre>");

   str = '{"name": "Joe", "age": 25, "group": null}';
   document.write("Input  = "+str+"\n");
   json = stringifier(JSON.parse(str));
   document.write("Output = "+json+"\n");

   str = '["first", {"name": "Jay", "age": 55, "group": "VIP"}]';
   document.write("Input  = "+str+"\n");
   json = stringifier(JSON.parse(str));
   document.write("Output = "+json+"\n");

   str = '["name", "Kim", "age", 30, "group", "Host"]';
   document.write("Input  = "+str+"\n");
   json = stringifier(JSON.parse(str));
   document.write("Output = "+json+"\n");

   document.write("</pre>");

</script>
</body>
</html>

Open the above code in a Web browser. You see the following output:

JSON.stringify() Replacer to Transform Values:

Input  = {"name": "Joe", "age": 25, "group": null}
Output = {"name":"Joe","group":null}
Input  = ["first", {"name": "Jay", "age": 55, "group": "VIP"}]
Output = ["first",{"name":"Jay","group":"VIP"}]
Input  = ["name", "Kim", "age", 30, "group", "Host"]
Output = ["name","Kim","age",30,"group","Host"]

⇒ JSON-stringify-space.html - JSON.stringify() Friendly Spaced

⇐ JSON-stringify-Transformed.html - JSON.stringify() Value Transformed

⇑ Using JSON in JavaScript

⇑⇑ JSON Tutorials