Vue HTTP Requests
The HTTP request is a part of the communication between a client and a server.
The client sends an HTTP request to the server, which handles the request and returns an HTTP response.
HTTP
HTTP stands for Hyper Text Transfer Protocol.
Our browser makes HTTP requests all the time in the background when we browse the Internet. When we access an Internet page, our browser (the client) sends several HTTP requests to make the server send us the page we want with all the relevant files and data as HTTP responses.
The most common kinds of HTTP requests are POST, GET, PUT, PATCH, and DELETE. Learn more about the different kinds of HTTP requests on our HTTP Request Methods page.
Learn more about what HTTP is on our What is HTTP page.
The 'fetch' Method
To get data from a server in Vue we can use the JavaScript fetch() method.
When we use the fetch() method in this tutorial we will not specify the HTTP request method, and that means that the default request method GET is what is used in the background.
The fetch() method expects a URL address as an argument so that it knows where to get the data from.
Here is a simple example that uses the fetch() method to send an HTTP GET request, and receive data as an HTTP response. The data requested in this case is the text inside the local file file.txt:
Example
App.vue:
<template>
<div>
<button @click="fetchData">Fetch Data</button>
<p v-if="data">{{ data }}</p>
</div>
</template>
<script>
export default {
data() {
return {
data: null,
};
},
methods: {
fetchData() {
const response = fetch("file.txt");
this.data = response;
}
}
};
</script>
In the example above, we only get "[object Promise]" as a result, but that is not what we want.
We get this result because fetch() is a promised-based method that returns a promise object. The first return the fetch() method gives is therefore just an object which means that the HTTP request has been sent. This is the "pending" state.
When the fetch() method actually gets the data we want, the promise is fulfilled.
To wait for the response to be fulfilled, with the data we want, we need to use the await operator in front of the fetch() method:
const response = await fetch("file.txt");
When the await operator is used inside a method, the method is required to be declared with the async operator:
async fetchData() {
const response = await fetch("file.txt");
this.data = response;
}
The async operator tells the browser that the method is asynchronous, which means that it waits for something, and the browser can continue to do other tasks while it waits for the method to complete.
Now what we get is a "Response", and no longer just a "Promise", which means we are one step closer to get the actual text inside the file.txt file:
Example
App.vue:
<template>
<div>
<button @click="fetchData">Fetch Data</button>
<p v-if="data">{{ data }}</p>
</div>
</template>
<script>
export default {
data() {
return {
data: null,
};
},
methods: {
async fetchData() {
const response = await fetch("file.txt");
this.data = response;
}
}
};
</script>
To get the text inside the file.txt file we need to use the text() method on the response. Because the text() method is a promise based method, we need to use the await operator in front of it.
Finally! We now have what we need to get the text from inside the file.txt file with the fetch() method:
Example
App.vue:
<template>
<div>
<button @click="fetchData">Fetch Data</button>
<p v-if="data">{{ data }}</p>
</div>
</template>
<script>
export default {
data() {
return {
data: null,
};
},
methods: {
async fetchData() {
const response = await fetch("file.txt");
this.data = await response.text();
}
}
};
</script>
Fetch Data from a JSON File
In the previous example we fetched text from a .txt file. But there are many ways to store data, and now we will see how we can fetch information from a .json file.
JSON is a common file format that is easy to work with because data is stored as text so that it is easy to read for humans, and the JSON format is also widely supported by programming languages, so that we can, for example, specify what data to extract from a .json file.
To read data from a .json file, the only change we need to do to the example above is to fetch a .json file, and use the json() method instead of the text() method on the response.
The json() method reads the response from the HTTP request and returns a JavaScript object.
We use the <pre> tag here to show the JSON formatted text because it preserves spaces and line breaks so that it is easier to read.
Example
App.vue:
<template>
<div>
<button @click="fetchData">Fetch Data</button>
<pre v-if="data">{{ data }}</pre>
</div>
</template>
<script>
export default {
data() {
return {
data: null,
};
},
methods: {
async fetchData() {
const response = await fetch("bigLandMammals.json");
this.data = await response.json();
}
}
};
</script>
Because the result of the json() method is a JavaScript object, we can modify the example above to show a random animal from the bigLandMammals.json file:
Example
App.vue:
<template>
<p>Try clicking the button more than once to see new animals picked randomly.</p>
<button @click="fetchData">Fetch Data</button>
<div v-if="randomMammal">
<h2>{{ randomMammal.name }}</h2>
<p>Max weight: {{ randomMammal.maxWeight }} kg</p>
</div>
</template>
<script>
export default {
data() {
return {
randomMammal: null
};
},
methods: {
async fetchData() {
const response = await fetch("bigLandMammals.json");
const data = await response.json();
const randIndex = Math.floor(Math.random()*data.results.length);
this.randomMammal = data.results[randIndex];
}
}
};
</script>
Data from an API
API stands for Application Programming Interface. You can learn more about API here.
There are a lot of interesting free APIs we can connect with and use, to get weather data, stock exchange data, etc.
The response we get when we call an API with an HTTP request can contain all kinds of data, but often contains data in the JSON format.
Example
A button can be clicked to get a random user from the random-data-api.com API.
App.vue:
<template>
<h1>Example</h1>
<p>Click the button to fetch data with an HTTP request.</p>
<p>Each click generates an object with a random user from <a href="https://random-data-api.com/" target="_blank">https://random-data-api.com/</a>.</p>
<p>The robot avatars are lovingly delivered by <a href="http://Robohash.org" target="_blank">RoboHash</a>.</p>
<button @click="fetchData">Fetch data</button>
<pre v-if="data">{{ data }}</pre>
</template>
<script>
export default {
data() {
return {
data: null,
};
},
methods: {
async fetchData() {
const response = await fetch("https://random-data-api.com/api/v2/users");
this.data = await response.json();
}
}
};
</script>
We can modify our previous example a little bit to include the random user in a more user friendly way:
Example
We show the random user name in a <pre> tag, along with the job title and image when the button is clicked.
App.vue:
<template>
<h1>Example</h1>
<p>Click the button to fetch data with an HTTP request.</p>
<p>Each click generates an object with a random user from <a href="https://random-data-api.com/" target="_blank">https://random-data-api.com/</a>.</p>
<p>The robot avatars are lovingly delivered by <a href="http://Robohash.org" target="_blank">RoboHash</a>.</p>
<button @click="fetchData">Fetch data</button>
<div v-if="data" id="dataDiv">
<img :src="data.avatar" alt="avatar">
<pre>{{ data.first_name + " " + data.last_name }}</pre>
<p>"{{ data.employment.title }}"</p>
</div>
</template>
<script>
export default {
data() {
return {
data: null,
};
},
methods: {
async fetchData() {
const response = await fetch("https://random-data-api.com/api/v2/users");
this.data = await response.json();
},
}
};
</script>
<style>
#dataDiv {
width: 240px;
background-color: aquamarine;
border: solid black 1px;
margin-top: 10px;
padding: 10px;
}
#dataDiv > img {
width: 100%;
}
pre {
font-size: larger;
font-weight: bold;
}
</style>
HTTP Request in Vue with The 'axios' Library
The 'axios' JavaScript library also allows us to make HTTP requests.
To create and run the example on your own machine you first need to install the 'axios' library using the terminal in your project folder, like this:
npm install axios
This is how we can use the 'axios' library in Vue to fetch a random user:
Example
Only small changes are made to the previous example to do the HTTP request with the 'axios' library instead.
App.vue:
<template>
<h1>Example</h1>
<p>Click the button to fetch data with an HTTP request.</p>
<p>Each click generates an object with a random user from <a href="https://random-data-api.com/" target="_blank">https://random-data-api.com/</a>.</p>
<p>The robot avatars are lovingly delivered by <a href="http://Robohash.org" target="_blank">RoboHash</a>.</p>
<button @click="fetchData">Fetch data</button>
<div v-if="data" id="dataDiv">
<img :src="data.data.avatar" alt="avatar">
<pre>{{ data.data.first_name + " " + data.data.last_name }}</pre>
<p>"{{ data.data.employment.title }}"</p>
</div>
</template>
<script>
import axios from 'axios'
export default {
data() {
return {
data: null,
};
},
methods: {
async fetchData() {
this.data = await axios.get("https://random-data-api.com/api/v2/users");
}
}
};
</script>
<style>
#dataDiv {
width: 240px;
background-color: aquamarine;
border: solid black 1px;
margin-top: 10px;
padding: 10px;
}
#dataDiv > img {
width: 100%;
}
pre {
font-size: larger;
font-weight: bold;
}
</style>
