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Node Modules — What does require() do?
Let's take a look at a small piece of code that we can easily turn into a Node.js module. Consider we have a method that allows us to drink tea.
function drinkTea() {
console.log("Mmm, delicious.");
}If this method was placed within a large JavaScript file, we could simply invoke the function
drinkTea() to enjoy a warm beverage. To create a module however, we simply place this function within its own file and tell Node about any functions we wish callers of the module to access.Within Node.js, we could therefore create a file called
drink.js with the following contents:function drinkTea() {
console.log("Mmm, delicious.");
}
module.exports.drinkTea = drinkTea;You'll notice that this file isn't that different from the original definition of our code. All that we've done to convert this code into a module is to add the
module.exports statement to the end of the file. This statement tells Node what methods to export from the module.From a different file, we could then load our tea drinking module and enjoy a cuppa by executing the following code:
var drinker = require('./drink');
drinker.drinkTea();The example above shows how to export and use a function from a module, but what if we want to export an object? Fortunately, the procedure here is exactly the same. We can create a
Tea object and export it from a Node module using the following code:var Tea = function(blend) {
this.blend=blend;
var that = this;
return {
drink: function() {
console.log('Mmm, '+ that.blend+ ', delicious.');
}
};
}
module.exports = Tea;We can then invoke this code from a separate
main module using code such as:var Tea = require('./drink');
var cupOfTea = new Tea('Assam');
cupOfTea.drink();>node main
Mmm, Assam, deliciousThe only difference here between the two examples is that in the first example, we exported a named function from our module (
module.exports.drinkTea = drinkTea). In the second example, we exported the object without any wrapper (module.exports = Tea). This allows us to directly create an instance of the module's Tea object, i.e. we can call new Tea... rather than new tea.Tea...Photo by Volodymyr Hryshchenko on Unsplash