Let's talk about exported functions, variables and modules in Node.js

Node.js is a JavaScript running environment based on the Chrome V8 engine. It allows JavaScript code to run on the server side, greatly improving the application capabilities of JavaScript on the server side.

In Node.js, we can use the exports object to export defined functions, variables, etc., so that they can be referenced by other modules. This article will introduce how to export functions, variables and modules in Node.js.

1. Export function

For example, we define a function:

function add(a, b) {
  return a + b;
}

To export this function, use the exports object in the module:

exports.add = function(a, b) {
  return a + b;
}

You can also use the following methods:

module.exports = function(a, b) {
  return a + b;
}

Both of the above two methods can export the add function. The specific method to use depends on the usage situation and personal habits.

2. Export variables

Export variables also use the exports object, for example:

exports.num = 123;

or:

module.exports.num = 123;

Both of the above methods can be used to convert num Variable export.

3. Export module

Sometimes, we need to export a module as a whole instead of exporting its functions or variables separately. At this time, we can use the module.exports object.

For example, we define a math module, which contains many mathematical functions:

function add(a, b) {
  return a + b;
}

function subtract(a, b) {
  return a - b;
}

function multiply(a, b) {
  return a * b;
}

function divide(a, b) {
  return a / b;
}

exports.add = add;
exports.subtract = subtract;
exports.multiply = multiply;
exports.divide = divide;

If we want to export the entire math module, we can use the module.exports object:

module.exports = {
  add: add,
  subtract: subtract,
  multiply: multiply,
  divide: divide
};

The above method will export an object containing add, subtract, multiply and divide functions. It should be noted that when using the module.exports object, you cannot use the exports object to export other functions or variables, otherwise it will be invalid.

Summary:

Through the above introduction, we have learned how to export functions, variables and modules in Node.js. Using Node.js to export modules can make our code more modular and efficient, and can also be easily called by other modules. In actual development, you can choose a suitable export method according to your needs to improve code reuse rate and development efficiency.

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