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Showing content from https://webplatform.github.io/docs/javascript/JSON/parse below:

parse · WebPlatform Docs

parse Summary

Converts a JavaScript Object Notation (JSON) string into an object.

Syntax

JSON.parse( text [ , reviver] )

text: Required. A valid JSON string.
reviver: Optional. A function that transforms the results. This function is called for each member of the object. If a member contains nested objects, the nested objects are transformed before the parent object is. For each member, the following occurs: If reviver returns a valid value, the member value is replaced with the transformed value.If reviver returns the same value it received, the member value is not modified.If reviver returns null or undefined , the member is deleted.

Return Value

An object or array.

Examples

The following example uses JSON.parse to convert a JSON string to an object.

var jsontext = '{"firstname":"Jesper","surname":"Aaberg","phone":["555-0100","555-0120"]}';
 var contact = JSON.parse(jsontext);
 document.write(contact.surname + ", " + contact.firstname);

The following example shows how to convert an array to a JSON string by using JSON.stringify , and then convert the string back to an array by using JSON.parse.

var arr = ["a", "b", "c"];
 var str = JSON.stringify(arr);
 document.write(str);
 document.write ("<br/>");

 var newArr = JSON.parse(str);

 while (newArr.length > 0) {
     document.write(newArr.pop() + "<br/>");
 }

 
 var arr = ["a", "b", "c"];
 var str = JSON.stringify(arr);
 document.write(str);
 document.write ("<br/>");

 var newArr = JSON.parse(str);

 while (newArr.length > 0) {
     document.write(newArr.pop + "<br/>");
 }

 
 ["a","b","c"]
 c
 b
 a

The reviver function is often used to transform JSON representation of International Organization for Standardization (ISO) date strings into Coordinated Universal Time (UTC) format Date objects.

This example uses JSON.parse to deserialize an ISO-formatted date string. The dateReviver function returns Date objects for members that are formatted like ISO date strings.

var jsontext = '{ "hiredate": "2008-01-01T12:00:00Z", "birthdate": "2008-12-25T12:00:00Z" }';
 var dates = JSON.parse(jsontext, dateReviver);
 document.write(dates.birthdate.toUTCString());

 function dateReviver(key, value) {
     var a;
     if (typeof value === 'string') {
         a = /^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2}(?:\.\d*)?)Z$/.exec(value);
         if (a) {
             return new Date(Date.UTC(+a[1], +a[2] - 1, +a[3], +a[4],
                             +a[5], +a[6]));
         }
     }
     return value;
 };

Exceptions

If this function provokes a JavaScript parser error (such as "SCRIPT1014: Invalid character", the input text does not comply with JSON syntax. To correct the error, do one of the following:

Modify the text argument to comply with JSON syntax. For more information, see the BNF syntax notation of JSON objects.
Make sure that the text argument was serialized by a JSON-compliant implementation, such as JSON.stringify.