Common JS Module Exports

Concepts in Focus

• Default Exports
• Exporting a variable while defining
• Exporting a variable after defining
• Exporting a value or an expression
• Exporting a function while defining
• Exporting a function after defining
• Exporting a class while defining
• Exporting a class after defining
• Named Exports
• Exporting multiple variables while defining
• Exporting multiple variables after defining
• Exporting multiple values and expressions
• Exporting multiple functions while defining
• Exporting multiple functions after defining
• Exporting multiple classes while defining
• Exporting multiple classes after defining

Let's see different scenarios that we may come across while exporting.

1. Default Exports

With Default Exports, we can import modules with any name.

1.1 Exporting a variable while defining

We cannot export boolean, number, string, null, undefined, objects, and arrays while defining.

Example:

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//sample.js

module.exports = let value = 5;

JAVASCRIPT

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//index.js

const num = require("./sample.js");

JAVASCRIPT

Output

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root@123# node index.js

/index.js:3

module.exports = let value = 5;

^

SyntaxError: Unexpected identifier

at wrapSafe (internal/modules/cjs/loader.js:1053:16)

...

1.2 Exporting a variable after defining

We can export boolean, number, string, null, undefined, objects, and arrays after defining.

Example:

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//sample.js

let value = 5;

module.exports = value;

JAVASCRIPT

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5

//index.js

const value = require("./sample.js");

console.log(value);

JAVASCRIPT

Output

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root@123# node index.js

5

1.3 Exporting a value or an expression

We can export a value or an expression directly.

Example:

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//sample.js

module.exports = 5 * 3;

JAVASCRIPT

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//index.js

const result = require("./sample.js");

console.log(result);

JAVASCRIPT

Output

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root@123# node index.js

15

1.4 Exporting a function while defining

We can export a function while defining.

Example:

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//sample.js

module.exports = function (num1, num2) {

return num1 + num2;

};

JAVASCRIPT

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//index.js

const sum = require("./sample.js");

console.log(sum(2, 6));

JAVASCRIPT

Output

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root@123# node index.js

8

1.5 Exporting a function after defining

We can export a function after defining.

Example:

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//sample.js

function sum(num1, num2) {

return num1 + num2;

}

module.exports = sum;

JAVASCRIPT

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//index.js

const sum = require("./sample.js");

console.log(sum(2, 6));

JAVASCRIPT

Output

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root@123# node index.js

8

1.6 Exporting a class while defining

We can export a class while defining.

Example:

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//sample.js

module.exports = class StudentDetails {

constructor(name, age) {

this.name = name;

this.age = age;

}

};

JAVASCRIPT

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//index.js

const StudentDetails = require("./sample.js");

const studentDetails = new StudentDetails("Ram", 15);

console.log(studentDetails);

console.log(studentDetails.name);

JAVASCRIPT

Output

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root@123# node index.js

StudentDetails { name: 'Ram', age: 15 }

Ram

1.7 Exporting a class after defining

We can export a class after defining.

Example:

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//sample.js

class StudentDetails {

constructor(name, age) {

this.name = name;

this.age = age;

}

}

module.exports = StudentDetails;

JAVASCRIPT

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//index.js

const StudentDetails = require("./sample.js");

const studentDetails = new StudentDetails("Ram", 15);

console.log(studentDetails);

console.log(studentDetails.name);

JAVASCRIPT

Output

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root@123# node index.js

StudentDetails { name: 'Ram', age: 15 }

Ram

2. Named Exports

2.1 Exporting multiple variables while defining

We cannot export boolean, number, string, null, undefined, objects, and arrays while defining.

Example:

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//sample.js

exports.value = let value = 5;

exports.studentName = let studentName = "Rahul";

JAVASCRIPT

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//index.js

const { value, studentName } = require("./sample");

console.log(value);

console.log(studentName);

JAVASCRIPT

Output

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root@123# node index.js

exports.value = let value = 5;

^^^^^

SyntaxError: Unexpected identifier

at wrapSafe (internal/modules/cjs/loader.js:1053:16)

2.2 Exporting multiple variables after defining

We can export multiple variables after defining.

Example:

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//sample.js

let value = 5;

exports.value = value;

let studentName = "Rahul";

exports.studentName = studentName;

JAVASCRIPT

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//index.js

const { value, studentName } = require("./sample");

console.log(value);

console.log(studentName);

JAVASCRIPT

Output

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root@123# node index.js

5

Rahul

2.3 Exporting multiple values and expressions

We can export multiple values and expressions.

Example:

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//sample.js

let value = 2;

exports.sum = 2 + 3;

exports.sub = 3 - value;

JAVASCRIPT

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//index.js

const { sum, sub } = require("./sample");

console.log(sum);

console.log(sub);

JAVASCRIPT

Output

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root@123# node index.js

5

1

2.4 Exporting multiple functions while defining

We can export multiple functions while defining.

Example:

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//sample.js

exports.sum = function (num1, num2) {

return num1 + num2;

};

exports.sub = function sub(num1, num2) {

return num1 - num2;

};

JAVASCRIPT

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//index.js

const { sum, sub } = require("./sample");

console.log(sum(2, 6));

console.log(sub(8, 3));

JAVASCRIPT

Output

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root@123# node index.js

8

5

2.5 Exporting multiple functions after defining

We can export multiple functions after defining.

Example:

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//sample.js

function sum(num1, num2) {

return num1 + num2;

}

exports.sum = sum;

function sub(num1, num2) {

return num1 - num2;

}

exports.sub = sub;

JAVASCRIPT

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//index.js

const { sum, sub } = require("./sample");

console.log(sum(2, 6));

console.log(sub(8, 3));

JAVASCRIPT

Output

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root@123# node index.js

8

5

2.6 Exporting multiple classes while defining

We can export multiple classes while defining.

Example:

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//sample.js

exports.studentDetails = class StudentDetails {

constructor(name, age) {

this.name = name;

this.age = age;

}

};

exports.carDetails = class CarDetails {

constructor(name, age) {

this.name = name;

this.speed = age;

}

};

JAVASCRIPT

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//index.js

const { studentDetails, carDetails } = require("./sample.js");

const newStudentDetails = new studentDetails("Ram", 15);

console.log(newStudentDetails);

console.log(newStudentDetails.name);

const newCarDetails = new carDetails("Alto", "60kmph");

console.log(newCarDetails);

console.log(newCarDetails.name);

JAVASCRIPT

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Output

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root@123# node index.js

StudentDetails { name: 'Ram', age: 15 }

Ram

CarDetails { name: 'Alto', speed: '60kmph' }

Alto

2.7 Exporting multiple classes after defining

We can export multiple classes after defining.

Example:

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//sample.js

class StudentDetails {

constructor(name, age) {

this.name = name;

this.age = age;

}

}

exports.studentDetails = StudentDetails;

class CarDetails {

constructor(name, age) {

this.name = name;

this.speed = age;

}

}

exports.carDetails = CarDetails;

JAVASCRIPT

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//index.js

const { studentDetails, carDetails } = require("./sample.js");

const newStudentDetails = new studentDetails("Ram", 15);

console.log(newStudentDetails);

console.log(newStudentDetails.name);

const newCarDetails = new carDetails("Alto", "60kmph");

console.log(newCarDetails);

console.log(newCarDetails.name);

JAVASCRIPT

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Output

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root@123# node index.js

StudentDetails { name: 'Ram', age: 15 }

Ram

CarDetails { name: 'Alto', speed: '60kmph' }

Alto