Convert JSON String into JavaScript Object

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In this tutorial, we are going to learn about how to convert a JSON string into JavaScript object with an example.
Learn more about JavaScript at https://www.javaguides.net/p/javascript-tutorial-with-examples.html

Usiing JSON.parse() Method

The JSON.parse() method parses a string and returns a JavaScript object. 

Here is a simple example using JSON.parse() method, which returns JavaScript object:
var text = JSON.parse( '{ "firstName" : "Ramesh", "lastName" : "Fadatare",  "emailId" : "[email protected]",  "age" : "29"  }');
console.log(text);
Output:
{firstName: "Ramesh", lastName: "Fadatare", emailId: "[email protected]", age: "29"}
Note that in the above example, we are passing JSON string to JSON.parse() method which returns JavaScript Object.

JSON.parse() Method - Detail Explanation

The JSON.parse() method parses a string and returns a JavaScript object. 

Syntax

JSON.parse(text[, reviver])

Parameter Values

  • text - This is a required field. A string is written in JSON format
  • reviver function - This parameter an optional. A function used to transform the result.
An optional reviver function can be provided to perform a transformation on the resulting object before it is returned.

JSON.parse() Method Examples

Here is a simple example using JSON.parse() method, which returns Javascript object:
var text = JSON.parse( '{ "firstName" : "Ramesh", "lastName" : "Fadatare",  "emailId" : "[email protected]",  "age" : "29"  }');
console.log(text);
Output:
{firstName: "Ramesh", lastName: "Fadatare", emailId: "[email protected]", age: "29"}
Note that the above javascript object is printed in the console.
How to use the reviver function:
/*replace the value of "city" to upper case:*/
var text = '{ "name":"John", "age":"39", "city":"New York"}';
var obj = JSON.parse(text, function (key, value) {
  if (key == "city") {
    return value.toUpperCase();
  } else {
    return value;
  }
});
console.log(text);
Output:
{ "name":"John", "age":"39", "city":"New York"}
More examples:
JSON.parse('{}');              // {}
JSON.parse('true');            // true
JSON.parse('"foo"');           // "foo"
JSON.parse('[1, 5, "false"]'); // [1, 5, "false"]
JSON.parse('null');            // null

Convert a JavaScript Object to JSON String

References

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