How to Store a JavaScript Fnction in JSON?

In JavaScript, we can store JavaScript functions in JSON objects, allowing us to serialize and store executable code alongside data. we will explore three approaches to store a JavaScript function in JSON.

These are the following approaches:

Using JSON.stringify()

In this approach, we are using JSON.stringify() to convert a JavaScript function func1 into a string representation using func1.toString(). This string representation is then stored in JSON object data with a key func1, and finally, the entire JSON object is converted into a JSON string jsonData.

Syntax:

JSON.stringify(value, replacer, space);

Example: The below example uses JSON.stringify to store a java script function in JSON.

JavaScript

const func1 = function() {
  console.log("Hello from GFG!");
};
const data = {
  func1: func1.toString()
};
const jsonData = JSON.stringify(data);
console.log(jsonData);

Output

{"func1":"function() {\n  console.log(\"Hello from GFG!\");\n}"}

Using a Custom toJSON() Method

In this approach, we are defining a JavaScript function func2 and creating a JSON object data that includes func2. We also implement a custom toJSON() method within data to specify how func2 should be converted to JSON using this.func2.toString(). When JSON.stringify(data) is called, it uses the custom toJSON() method to convert func2 into a string representation and include it in the resulting JSON string jsonData.

Example: The below example uses the Custom toJSON() Method to store a JavaScript function in JSON.

JavaScript

const func2 = function() {
  console.log("Hello from GFG!");
};
const data = {
  func2,
  toJSON: function() {
    return {
      func2: this.func2.toString()
    };
  }
};
const jsonData = JSON.stringify(data);
console.log(jsonData); 

Output

{"func2":"function() {\n  console.log(\"Hello from GFG!\");\n}"}

Using a replacer Function in JSON.stringify()

In this approach, JSON.stringify() is used with a replacer function that checks if a value is a function, converting it into a string with toString(), enabling the storage of JavaScript function func3 in JSON format with proper string representation.

Syntax:

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

Example: The below example uses the replacer Function in JSON.stringify() to store a JavaScript function in JSON.

JavaScript

const func3 = function() {
  console.log("Hello from GFG!");
};
const jsonData = JSON.stringify({ func3 },
                      function(key, value) {
  if (typeof value === 'function') {
    return value.toString();
  }
  return value;
});
console.log(jsonData); 

Output

{"func3":"function() {\n  console.log(\"Hello from GFG!\");\n}"}