How to Convert an Object to a JSON String in Typescript ?

In TypeScript, an object is a collection of related data and functionality. Objects are made up of properties and methods. Properties describe the object, methods describe what it can do.

Using JSON.stringify()

• Define an interface Course that describes the shape of the object with the required properties and their types.
• Declare the course variable with the Course type. This ensures the object matches the interface shape.
• Assign the object literal to the course – TypeScript will check it matches the interface.
• Call JSON.stringify() on the typed object.

Example: The below code will explain the use of the JSON.stringify() method to convert an object to JSON string.

Javascript

interface Course {
    courseName: string;
    courseFees: number;
}

const course: Course = {
    courseName: "Javascript",
    courseFees: 30000,
};

const jsonString = JSON.stringify(course);

console.log(jsonString);

Output:

{
    "courseName": "Javascript",
    "courseFees": 30000
}

Using json-stringify-safe library

Steps to use JSON-stringify-safe library with TypeScript:

Step 1: Initialize a New Project

Open your terminal or command prompt and navigate to the directory where you want to create your TypeScript project. Then run the following command.

npm init

Step 2: Install TypeScript as a dev dependency

You need to install TypeScript as a dev dependency in your project using the below command.

npm install typescript --save-dev

Step 3: Create a tsconfig.json file

The tsconfig.json file contains TypeScript compiler options for your project. Run the following command.

npx tsc --init

Step 4: Install json-stringify-safe

Install the JSON-stringify-safe library using the below command.

npm install json-stringify-safe

Step 5: Install node types

Install the @types/node into your project directory using the below command.

npm install --save @types/node

Step 6: Compile TypeScript Code

Use below command to compile TypeScript code.

npx tsc index.ts

Step 7: Run Your Code

Use the below command to run the code.

node index

Project Structure:

project structure

Example: The below code uses JSON-stringify-safe library to convert an object into JSON string.

Javascript

// index.ts
const stringifySafe = 
    require('json-stringify-safe');

interface Course {
    courseName: string;
    courseFees: number;
}
const course: Course = {
    courseName: 'Javascript',
    courseFees: 30000
}
const jsonString: string = 
    stringifySafe(course);
console.log(jsonString);

Output:

{
    "courseName": "Javascript",
    "courseFees": 30000
}

Using a Custom Serialization Function

In some cases, you may have complex objects with nested structures or non-serializable properties that need special handling when converting to JSON. In such scenarios, you can define a custom serialization function to handle the conversion process.

Example:

JavaScript

interface Course {
    courseName: string;
    courseFees: number;
    startDate: Date;
}

const course: Course = {
    courseName: "JavaScript",
    courseFees: 30000,
    startDate: new Date("2024-03-01"),
};

function customStringify(obj: any): string {
    return JSON.stringify(obj, (key, value) => {
        if (value instanceof Date) {
        // Serialize Date objects to ISO string
            return value.toISOString(); 
        }
        return value;
    });
}

const jsonString = customStringify(course);
console.log(jsonString);

Output:

{"courseName":"JavaScript","courseFees":30000,"startDate":"2024-03-01T00:00:00.000Z"}