Convert a JavaScript Object to JSON String

In this tutorial, we are going to learn about how to convert a JavaScript object to a JSON string.

Learn more about JavaScript at https://www.javaguides.net/p/javascript-tutorial-with-examples.html

Using JSON.stringify() Method

In JavaScript, we have a JSON.stringify() method which is used to convert an object into a string.

Consider we have a JavaScript object like:

  var user = {
    firstName : 'Ramesh',
    lastName : 'Fadatare',
    emailId : '[email protected]',
    age : 29
  }

Now we need to convert the above object into a string by using JSON.stringy() method.

Convert above Javascript object into JSON string as:

JSON.stringify(user)
console.log(JSON.stringify(user));

Output:

{"firstName":"Ramesh","lastName":"Fadatare","emailId":"[email protected]","age":29}

JSON.stringify() Method - Detail Explanation

The JSON.stringify() method converts a JavaScript object or value to a JSON string, optionally replacing values if a replacer function is specified or optionally including only the specified properties if a replacer array is specified.

Syntax

JSON.stringify(value[, replacer[, space]])

Parameters

• value - This is a parameter is required. The value to convert to a JSON string.
• replacer - This parameter is optional. Either a function or an array used to transform the result. The replacer is called for each item.
• space - This parameter is optional. A String or Number object that's used to insert white space into the output JSON string for readability purposes.

JSON.stringify() Method Examples

Example 1: Let's create a Javascript object:

  var user = {
    firstName : 'Ramesh',
    lastName : 'Fadatare',
    emailId : '[email protected]',
    age : 29
  }

Convert above Javascript object into JSON string as:

JSON.stringify(user)
console.log(JSON.stringify(user));

Output:

{"firstName":"Ramesh","lastName":"Fadatare","emailId":"[email protected]","age":29}

Example 2: replacer argument example, as a function

function replacer(key, value) {
  // Filtering out properties
  if (typeof value === 'string') {
    return undefined;
  }
  return value;
}

var foo = {foundation: 'Mozilla', model: 'box', week: 45, transport: 'car', month: 7};
JSON.stringify(foo, replacer);

Output:

"{"week":45,"month":7}"

Example 3: replacer argument example, as an array

If replacer is an array, the array's values indicate the names of the properties in the object that should be included in the resulting JSON string.

var foo = {foundation: 'Mozilla', model: 'box', week: 45, transport: 'car', month: 7};
JSON.stringify(foo, ['week', 'month']);  

Output:

"{"week":45,"month":7}"

Example 4: The space argument example. The space argument may be used to control spacing in the final string.

JSON.stringify({ a: 2 }, null, ' ');

Output:

"{
 "a": 2
}"

Using a tab character mimics standard pretty-print appearance:

JSON.stringify({ uno: 1, dos: 2 }, null, '\t');

Output:

"{
 "uno": 1,
 "dos": 2
}

References

• https://www.javaguides.net/p/javascript-tutorial-with-examples.html

• https://www.javaguides.net/2019/04/javascript-json-methods-guide.html