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Difference between a Library and a Framework

Both frameworks and libraries are code written by someone else that is used to help solve common problems. For example, let’s say you have a program where you plan on working with strings. You decide to keep your code DRY (don’t repeat yourself) and write some reusable functions like these:

function getWords(str) {
   const words = str.split(' ');
   return words;
}

function createSentence(words) {
   const sentence = words.join(' ');
   return sentence;
}

Congratulations. You’ve created a library. Let's use a house as a metaphor for understanding: A library is like going to Ikea. You already have a home, but you need a bit of help with furniture. You don’t feel like making your own table from scratch. Ikea allows you to pick and choose different things to go in your home. You are in control.

A framework, on the other hand, is like building a model home. You have a set of blueprints and a few limited choices when it comes to architecture and design. Ultimately, the contractor and blueprint are in control. And they will let you know when and where you can provide your input.

The Technical Difference

The technical difference between a framework and library lies in a term called ‘inversion of control’. When you use a library, you are in charge of the flow of the application. You are choosing when and where to call the library. When you use a framework, the framework is in charge of the flow. It provides some places for you to plug in your code, but it calls the code you plugged in as needed.