On top of that you'll also learn how to think differently about _how_ you write your programs. Like in any field, once you've mastered a particular way of doing things you start thinking about how it could be done in a smarter, different way. In programming we call these `paradigms` and in this module you'll learn one such paradigm: Object-Oriented Programming!

If you have any questions or if something is not entirely clear ¯\_(ツ)\_/¯, please ask/comment on Slack!

- An example of a library

- How to use a library

Whenever we talk about software development, we'll inevitably end up talking about `Application Programming Interfaces`, or APIs for short. But what is all the fuss about?

xhr.send();

if (xhr.status != 200) {

// analyze HTTP status of the response

alert(`Error ${xhr.status}: ${xhr.statusText}`); // e.g. 404: Not Found

}

};

if (event.lengthComputable) {

alert(`Received ${event.loaded} of ${event.total} bytes`);

} else {

alert(`Received ${event.loaded} bytes`); // no Content-Length

}

};

alert('Request failed');

};

axios

.get('https://pokeapi.co/api/v2/pokemon')

console.log(response);

// Do something with data

})

console.log(error);

// Do something with error

});

- 'this' keyword

4. Fetch API

You are undoubtedly different than when you were a baby. Back then you couldn't do much except crying. That's pretty much it. But as the years pass you increasingly could do more and more: walking, socializing or playing an instrument.

This is where `Promises` come in. The idea of the `Promise` is a product of the evolution within the JavaScript language. A bunch of JavaScript developers wanted to figure out how to solve the problem of callback hell and this is what they came up with. Here's a basic example:

if (true) {

resolve('It has succeeded!');

} else {

What if you need to perform several asynchronous operations, that depend on the result of the one that came before it? For that we can use the `.then()` method: a special function, given to us by the Promise object, that allows us to directly use the return value of the asynchronous operation that happened before. Here's an example:

setTimeout(() => resolve(1), 1000); // We wait 1 second and then resolve with value 1

})

console.log(result); // Result: 1

return result * 2;

})

alert(result); // Result: 2

return result * 2;

})

console.log(error);

});

const wouter = {

firstName: 'Wouter',

lastName: 'Kleijn',

return this.firstName + ' ' + this.lastName;

},

};

fetch('https://pokeapi.co/api/v2/pokemon')

return response.json();

})

console.log('Pokemon data', data);

return data;

})

console.log('err', error);

});

- Catching errors with try/catch

4. Thinking like a programmer III

So far we've learned about various programming concepts. These are the basics of what makes up any application: it's the **WHAT** of writing applications. However, now that you're familiar with them it's time to go to the next level: the **HOW** of writing applications.

const numbers = [14, 5, 25, 8];

return number < 10;

});

};

var obj = {

name: name,

age: age,

console.log(`${this.name} is walking!`);

},

};

In the Promise object, we can use the function `catch` to take care of errors. It takes in a callback, which automatically receives an error object. Here's an example:

console.log(error);

});

There are many ways to write clean code. Some of them you might have heard: Don't Repeat Yourself (DRY) or Keep It Simple, Stupid (KISS) are two things to keep in mind. There are many others and you are encouraged to do your own research!

Here are already a couple of them to get you started:

- [Top 5 Programming Principles that any software engineer should follow](https://www.youtube.com/watch?v=d-KbEQM0724)

- [Programming Terms: DRY (Don't Repeat Yourself)](https://www.youtube.com/watch?v=IGH4-ZhfVDk)

- [The KISS Principle in Software Development — Everything You Need to Know](https://medium.com/@devisha.singh/the-kiss-principle-in-software-development-everything-you-need-to-know-dd8ea6e46bcd)