2 min readMar 28


According to the MDN Web Docs “ A promise is a proxy for a value not necessarily known “. In other words, a promise is an intermediary between the web application and the server.

How does a Promise work?

To understand how a promise works let’s analyze the fetch function. Fetch is a JavaScript function for performing HTTP requests. And when we make an HTTP request the first thing fetch() returns us is a promise object with a status of pending, because the fetch is making us a “promise” that the request was made and that it will return us with the server’s response.

fetch('') .then( console.log(response.json()))

Then the second return is effectively the server response

fetch('') .then( console.log(response.json())) .then( console.log(json))

Why use?

1- Simplified Error Management: Promises allow you to catch errors in an easier and more organized way compared to nested callbacks. Instead of dealing with multiple levels of nested callbacks, Promises can use a single function catch() to handle all errors in one place.

2- More readability and less nesting: Using Promises can improve code readability as Promises allow code to be written in a more logical and linear sequence rather than using nested callbacks which can make code difficult to read . This can make the code easier to understand and maintain.

3- More modular and reusable code: Promises can be easily used in multiple places in the code and can be chained together to create control flows in a modular way. This makes the code more reusable and easier to maintain and update over time. Additionally, Promises can be used in conjunction with other JavaScript functionality such as async/await to create more efficient and cleaner code.

In other articles we will talk more about synchronous functions with async/await.




Full Stack Developer (JavaScript | Python | Go). Graduanda em Ciências Matemáticas e da Terra (UFRJ) e se arriscando na área de Ciência de Dados e IA (só pelo r