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In this post, I show you how to parse JSON string into particular JavaScript Object or Constructor Function (i.e. with a certain prototype).

JavaScript provides JSON.parse() API to parse JSON string into a JavaScript object. But in this post, I show you how to parse JSON string into a JavaScript object prototype using a constructor function.

Parse JSON String into JavaScript Object Prototype or Constructor Function

Let's create a JavaScript constructor function:

function Post(){
    this.id = "";
    this.title = "";
    this.description = "";
    this.postedUser = new User();
}

function User(){
    this.id="";
    this.name = "";
    this.age = "";
}

To test, we need to create a JSON object in JavaScript like:

var json2 = {
    "post" : {
        "id" : "1",
        "title" : "post title",
        "description" : "post description",
        "postedUser" : {
            "id" : "1",
            "name" : "Ramesh",
            "age" : "29"
        }
    }
}

Now, we create a JavaScript function to parse above JSON into a JavaScript object:

function demo(){
    // parse to json string
    var jsonStr = JSON.stringify(json2);

    // parse json string into JavaScript Object
    var object = JSON.parse(jsonStr);

    console.log(object);
    console.log(object.getTitle());
}

demo();

Complete Code and Output

function Post(){
    this.id = "";
    this.title = "";
    this.description = "";
    this.postedUser = new User();
}

function User(){
    this.id="";
    this.name = "";
    this.age = "";
}

var json2 = {
    "post" : {
        "id" : "1",
        "title" : "post title",
        "description" : "post description",
        "postedUser" : {
            "id" : "1",
            "name" : "Ramesh",
            "age" : "29"
        }
    }
}

function demo(){
    // parse to json string
    var jsonStr = JSON.stringify(json2);

    // parse json string into JavaScript Object
    var object = JSON.parse(jsonStr);

    console.log(object);
    console.log(object.getTitle());
}

demo();

For the best learning experience, I highly recommended that you open a console (which, in Chrome and Firefox, can be done by pressing Ctrl+Shift+I), navigate to the "console" tab, copy-and-paste each JavaScript code example from this article, and run it by pressing the Enter/Return key.