SvelteKit GraphQL Queries using fetch Only # SvelteKit GraphQL Queries using fetch Only #

API Key #

We will be using the SWOP GraphQL API  to pull the latest available currency exchange rates. To use the service, we will need an API key. There is a free developer tier, and they only ask for an email address when signing up. Let's go to the sign-up page now, sign up , confirm our email address and then make a note of our new API key.

Configuring Environment Variables #

Create a .env file in the project root folder containing your API key:

    
SWOP_API_KEY="0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"

  

With the preliminaries out of the way, let’s write our query.

🧱 API Route #

To create a GraphQL query using fetch, basically all you need to do is create a query object and a variables object, convert them to a string and then send them as the body to the right API endpoint. We will use fetch to do the sending as it is already included in SvelteKit though you could choose axios or some other package if you wanted to. In addition to the body, we need to make sure we include the right auth headers (as you would with Apollo client or urql).

That’s enough theory. If you want to do some more reading, Jason Lengstorf from Netlify wrote a fantastic article  with plenty of extra details.

Let’s write some code. Create a file at src/routes/+page.server.ts and paste in the following code:

    
1 import { SWOP_API_KEY } from '$env/static/private';
2 import type { Query, QueryLatestArgs } from '$lib/generated/graphql';
3 import { error } from '@sveltejs/kit';
4 import type { Actions, PageServerLoad } from './$types';
5 
6 const query = `
7 query latestQuery(
8 	$baseCurrency: String = "EUR"
9 	$quoteCurrencies: [String!]
10 ) {
11 	latest(
12 		baseCurrency: $baseCurrency
13 		quoteCurrencies: $quoteCurrencies
14 	) {
15 		baseCurrency
16 		quoteCurrency
17 		date
18 		quote
19 	}
20 }
21 `;
22 
23 export const load: PageServerLoad = async () => {
24 	try {
25 		const variables: QueryLatestArgs = {
26 			baseCurrency: 'EUR',
27 			quoteCurrencies: ['CAD', 'GBP', 'IDR', 'INR', 'USD']
28 		};
29 
30 		const response = await fetch('https://swop.cx/graphql', {
31 			method: 'POST',
32 			headers: {
33 				'Content-Type': 'application/json',
34 				Authorization: `ApiKey ${SWOP_API_KEY}`
35 			},
36 			body: JSON.stringify({
37 				query,
38 				variables
39 			})
40 		});
41 
42 		const { data: responseData }: { data: Query } = await response.json();
43 
44 		return { ...responseData };
45 	} catch (error) {
46 		console.error(`Error in load function for /: ${error}`);
47 	}
48 };

  

What this Code Does #

You can see in lines 6 – 21 we define the GraphQL query. This uses regular GraphQL syntax. Just below, we define our query variables. If you are making a different query which does not need any variables, be sure to include an empty variables object.

In line 30 you see we make a fetch request to the SWOP API. Importantly, we include the Content-Type header, set to application/json in line 33. The rest of the file just processes the response and relays it to the client.

Let’s create a store to save retrieved data next.

🛍 Store #

We will create a store as our “single source of truth”. Stores are an idiomatic, Svelte way of sharing app state between components. We won't go into much detail here, and you can learn more about Svelte stores in the Svelte tutorial .

To build the store, all we need to do is create the following file. Let's do that now, pasting the content below into src/lib/shared/stores/rates.ts (you will need to create new folders):

    
1 import { writable } from 'svelte/store';
2  
3 const rates = writable([]);
4  
5 export { rates as default };

  

Next, we can go client side to make use of SvelteKit GraphQL queries using fetch only.

🖥 Initial Client Code: SvelteKit GraphQL queries using fetch #

We are using TypeScript in this project, but very little, so hopefully you can follow along even though you are not completely familiar with TypeScript. Replace the content of src/routes/+page.svelte with the following:

    
1 <script lang="ts">
2 	import rates from '$lib/shared/stores/rates';
3 	import '@fontsource/source-sans-pro/latin.css';
4 	import type { ActionData, PageData } from './$types';
5 
6 	export let data: PageData;
7 
8 	data.latest && rates.set(data.latest);
9 </script>
10 
11 <main class="container">
12 	<div class="heading">
13 		<h1>FX Rates</h1>
14 	</div>
15 	<ul class="content">
16 		{#each $rates as { baseCurrency, quoteCurrency, date, quote }}
17 			<li>
18 				<h2>{`${baseCurrency}\${quoteCurrency}`}</h2>
19 				<dl>
20 					<dt>
21 						{`1 ${baseCurrency}`}
22 					</dt>
23 					<dd>
24 						<span class="rate">
25 							{quote.toFixed(2)}
26 							{quoteCurrency}
27 						</span>
28 						<details><summary>More information...</summary>Date: {date}</details>
29 					</dd>
30 				</dl>
31 			</li>
32 		{/each}
33 	</ul>
34 
35 	<form method="POST">
36 		<span class="screen-reader-text"
37 			><label for="additional-currency">Additional Currency</label></span
38 		>
39 		<input
40 			required
41 			id="additional-currency"
42 			name="currency"
43 			placeholder="AUD"
44 			title="Add another currency"
45 			type="text"
46 		/>
47 		<button type="submit">Add currency</button>
48 	</form>
49 </main>

  

What are we Doing Here? #

The export let data in line 6 is telling SvelteKit to source the data parameter from the page load function (we will create this in a moment). This contains the initial rate data we got from the GraphQL query.

At line 3, we import the store we just created. Next, we actually make use of the store. We add the query result to the store in line 16. We will actually render whatever is in the store, rather than the result of the query directly. The benefit of doing it that way is that we can easily update what is rendered by adding another other currency pair to the store (without any complex logic for merging what is already rendered with new query results). You will see this shortly.

Optional Styling #

This should all work as is. Optionally add a little style before continuing:

    
51 <style>
52 	:global body {
53 		margin: 0px;
54 	}
55 
56 	.container {
57 		display: flex;
58 		flex-direction: column;
59 		background: #ff6b6b;
60 		min-height: 100vh;
61 		color: #1a535c;
62 		font-family: 'Source Sans Pro';
63 	}
64 
65 	.content {
66 		margin: 3rem auto 1rem;
67 		width: 50%;
68 		border-radius: 1rem;
69 		border: #f7fff7 solid 1px;
70 	}
71 
72 	.heading {
73 		background: #f7fff7;
74 		text-align: center;
75 		width: 50%;
76 		border-radius: 1rem;
77 		border: #1a535c solid 1px;
78 		margin: 3rem auto 0rem;
79 		padding: 0 1.5rem;
80 	}
81 
82 	h1 {
83 		color: #1a535c;
84 	}
85 
86 	ul {
87 		background: #1a535c;
88 		list-style-type: none;
89 		padding: 1.5rem;
90 	}
91 
92 	li {
93 		margin-bottom: 1.5rem;
94 	}
95 
96 	h2 {
97 		color: #ffe66d;
98 		margin-bottom: 0.5rem;
99 	}
100 
101 	dl {
102 		background-color: #ffe66d;
103 		display: flex;
104 		margin: 0.5rem 3rem 1rem;
105 		padding: 1rem;
106 		border-radius: 0.5rem;
107 		border: #ff6b6b solid 1px;
108 	}
109 
110 	.rate {
111 		font-size: 1.25rem;
112 	}
113 	dt {
114 		flex-basis: 15%;
115 		padding: 2px 0.25rem;
116 	}
117 
118 	dd {
119 		flex-basis: 80%;
120 		flex-grow: 1;
121 		padding: 2px 0.25rem;
122 	}
123 
124 	form {
125 		margin: 1.5rem auto 3rem;
126 		background: #4ecdc4;
127 		border: #1a535c solid 1px;
128 		padding: 1.5rem;
129 		border-radius: 1rem;
130 		width: 50%;
131 	}
132 	input {
133 		font-size: 1.563rem;
134 		border-radius: 0.5rem;
135 		border: #1a535c solid 1px;
136 		background: #f7fff7;
137 		padding: 0.25rem 0.25rem;
138 		margin-right: 0.5rem;
139 		width: 6rem;
140 	}
141 	button {
142 		font-size: 1.563rem;
143 		background: #ffe66d;
144 		border: #1a535c solid 2px;
145 		padding: 0.25rem 0.5rem;
146 		border-radius: 0.5rem;
147 		cursor: pointer;
148 	}
149 
150 	.screen-reader-text {
151 		border: 0;
152 		clip: rect(1px, 1px, 1px, 1px);
153 		clip-path: inset(50%);
154 		height: 1px;
155 		margin: -1px;
156 		width: 1px;
157 		overflow: hidden;
158 		position: absolute !important;
159 		word-wrap: normal !important;
160 	}
161 
162 	@media (max-width: 768px) {
163 		.content,
164 		form,
165 		.heading {
166 			width: auto;
167 			margin: 1.5rem;
168 		}
169 	}
170 </style>

  

OK, let’s take a peek at what we have so far by going to localhost:5173/.

🚀 SvelteKit GraphQL queries using fetch: Updating the Store #

Finally, we will look at how updating the store updates the user interface. We already have a form in src/routes/+page.svelte (lines 35 – 48), but it is not yet wired up. We already have a name attribute set on the input. We can use this, now, in our action code, to pull in whatever the user enters. Update src/routes/+page.server.ts:

    
1 import { SWOP_API_KEY } from '$env/static/private';
2 import type { Query, QueryLatestArgs } from '$lib/generated/graphql';
3 import { error } from '@sveltejs/kit';
4 import type { Actions, PageServerLoad } from './$types';
5 
6 const query = `
7 query latestQuery(
8 	$baseCurrency: String = "EUR"
9 	$quoteCurrencies: [String!]
10 ) {
11 	latest(
12 		baseCurrency: $baseCurrency
13 		quoteCurrencies: $quoteCurrencies
14 	) {
15 		baseCurrency
16 		quoteCurrency
17 		date
18 		quote
19 	}
20 }
21 `;
22 
23 export const actions: Actions = {
24 	default: async ({ request }) => {
25 		try {
26 			const form = await request.formData();
27 			const currency = form.get('currency');
28 
29 			if (typeof currency === 'string') {
30 				const variables: QueryLatestArgs = {
31 					baseCurrency: 'EUR',
32 					quoteCurrencies: [currency]
33 				};
34 
35 				const response = await fetch('https://swop.cx/graphql', {
36 					method: 'POST',
37 					headers: {
38 						'Content-Type': 'application/json',
39 						Authorization: `ApiKey ${SWOP_API_KEY}`
40 					},
41 					body: JSON.stringify({
42 						query,
43 						variables
44 					})
45 				});
46 
47 				const responseData: { data: Query } = await response.json();
48 				const rate = responseData.data.latest[0];
49 
50 				return { rate };
51 			}
52 			return undefined;
53 		} catch (err: unknown) {
54 			const message = `Error in /login form: ${err as string}`;
55 			console.error(message);
56 			return error(500, message);
57 		}
58 	}
59 };
60 
61 export const load: PageServerLoad = async () => {
62 	try {
63 		const variables: QueryLatestArgs = {
64 			baseCurrency: 'EUR',
65 			quoteCurrencies: ['CAD', 'GBP', 'IDR', 'INR', 'USD']
66 		};
67 
68 		const response = await fetch('https://swop.cx/graphql', {
69 			method: 'POST',
70 			headers: {
71 				'Content-Type': 'application/json',
72 				Authorization: `ApiKey ${SWOP_API_KEY}`
73 			},
74 			body: JSON.stringify({
75 				query,
76 				variables
77 			})
78 		});
79 
80 		const { data: responseData }: { data: Query } = await response.json();
81 
82 		return { ...responseData };
83 	} catch (error) {
84 		console.error(`Error in load function for /: ${error}`);
85 	}
86 };

  

In lines 26 – 27, we read in the form data, identifying the field we need using the value of its name field (currency). After that, the code is not that different from the load function that already existed in this file. The main difference is that we query for and return a single rate, rather than an array of rates, as in the load function.

We need to read this in the client, Svelte, file. Update src/routes/+page.svelte with these lines so, once the user submits the form, we trigger a store update:

    
1 <script lang="ts">
2 	import rates from '$lib/shared/stores/rates';
3 	import '@fontsource/source-sans-pro/latin.css';
4 	import type { ActionData, PageData } from './$types';
5 
6 	export let data: PageData;
7 	export let form: ActionData;
8 
9 	data.latest && rates.set(data.latest);
10 	 
11 	if (form?.rate) {
12 		rates.set([...$rates, form.rate]);
13 	}
14 </script>
15 
16 <main class="container">
17 	<div class="heading">
18 		<h1>FX Rates</h1>
19 	</div>
20 	<ul class="content">
21 		{#each $rates as { baseCurrency, quoteCurrency, date, quote }}
22 			<li>
23 				<h2>{`${baseCurrency}\${quoteCurrency}`}</h2>
24 				<dl>
25 					<dt>
26 						{`1 ${baseCurrency}`}
27 					</dt>
28 					<dd>
29 						<span class="rate">
30 							{quote.toFixed(2)}
31 							{quoteCurrency}
32 						</span>
33 						<details><summary>More information...</summary>Date: {date}</details>
34 					</dd>
35 				</dl>
36 			</li>
37 		{/each}
38 	</ul>
39 
40 	<form method="POST">
41 		<span class="screen-reader-text"
42 			><label for="additional-currency">Additional Currency</label></span
43 		>
44 		<input
45 			required
46 			id="additional-currency"
47 			name="currency"
48 			placeholder="AUD"
49 			title="Add another currency"
50 			type="text"
51 		/>
52 		<button type="submit">Add currency</button>
53 	</form>
54 </main>

  

Try this out yourself, adding a couple of currencies. The interface should update straight away.

🙌🏽 SvelteKit GraphQL queries using fetch: What Do You Think? #

In this post, we learned:

• how to do SvelteKit GraphQL queries using fetch instead of Apollo client or urql,
• a way to get up-to-date currency exchange rate information into your site backend dashboard for analysis, accounting, and so many other uses,
• how stores can be used in Svelte to update state.

See the follow-up post in which we automatically generate TypeScript types for the GraphQL API. Type generation is not too onerous in this example, though you can see how to do it automatically for more intricate GraphQL APIs, getting free autocompletion and help to spot code errors.

There are some restrictions on the base currency in SWOP's developer mode. The maths (math) to convert from EUR to the desired base currency isn't too complicated, though. You could implement a utility function to do the conversion in the API route file. If you do find the service useful, or and expect to use it a lot, consider supporting the project by upgrading your account.

Extensions #

As an extension you might consider pulling historical data from the SWOP API, this is not too different, to the GraphQL query above. Have play in the SWOP GraphQL Playground to discover more of the endless possibilities . Finally, you might also find the Purchasing Power API  handy if you are looking at currencies. This is not a GraphQL API, though it might be quite helpful for pricing your courses in global economies you are not familiar with.

Is there something from this post you can leverage for a side project or even client project? I hope so! Let me know if there is anything in the post that I can improve on, for anyone else creating this project. You can leave a comment below, @ me on Twitter  or try one of the other contact methods listed below.

You can see the full code for this SvelteKit GraphQL queries using fetch project on the Rodney Lab Git Hub repo .

🏁 SvelteKit GraphQL queries using fetch: Summary #

Do you need to use Apollo Client or urql to run GraphQL queries in SvelteKit? #

SvelteKit makes fetch available in load functions and on endpoints. This is a great alternative to Apollo Client and urql when you want to get up and running quickly on your new project. Although you won't have access to the caching features provided by Apollo Client and urql if you use just fetch, SvelteKit does make it easy to create a cache using stores. The advantages of using fetch are you keep your app lighter, with fewer dependencies, and also that the API is very stable. This saves you refactoring code as APIs change.

How do you use fetch for GraphQL queries in SvelteKit? #

Using fetch for GraphQL queries is as simple as creating a query and variables object and sending those to your endpoint. In the case your query does not need any variables, you will still need to include an albeit empty variable object in the request. The query variable is the GraphQL query (or mutation) using regular GraphQL syntax, as a string. We use the POST method to send the query to our external API. Importantly, we include the 'Content-Type': 'application/json' HTTP header in the request.

Where can I find some example code using fetch for GraphQL queries in SvelteKit? #

In this tutorial, we run through an example using an FX rate GraphQL API to fetch data. We make GraphQL calls both from the client code and our API endpoints. There is also a link to the complete tutorial project code on GitHub at the bottom of the article. You can follow along, building the project out yourself, or just jump straight to the GitHub repo.

🙏🏽 SvelteKit GraphQL queries using fetch: Feedback #

Have you found the post useful? Do you have your own methods for solving this problem? Let me know your solution. Would you like to see posts on another topic instead? Get in touch with ideas for new posts. Also, if you like my writing style, get in touch if I can write some posts for your company site on a consultancy basis. Read on to find ways to get in touch, further below. If you want to support posts similar to this one and can spare a few dollars, euros or pounds, please consider supporting me through Buy me a Coffee.

Rodney

@askRodney

🔥 Here's something to help you keep your SvelteKit GraphQL apps lean.

See how you can query

#GraphQL endpoints using just fetch... no urql, no Apollo client!

Also handle state with ❤️ Svelte stores.

Hope you find this useful!https://t.co/D1rLmh229H #sveltekit @SvelteSociety pic.twitter.com/087gRALZxq

— Rodney (@askRodney) September 27, 2021

Finally, feel free to share the post on your social media accounts for all your followers who will find it useful. As well as leaving a comment below, you can get in touch via @askRodney on Twitter and also askRodney on Telegram . Also, see further ways to get in touch with Rodney Lab. I post regularly on SvelteKit as well as other topics. Also, subscribe to the newsletter to keep up-to-date with our latest projects.