RxJS loading indicator on any ajax request - ajax

Question

I need to show a loading indicator any time an ajax request occurs. Based on this question RxJs How to set default request headers? I believe I'll have to create an ajax wrapper to use.
My requirements are to start the loading indicator when a request occurs. It can start again if there is already a request running. When a request completes/errors, I need the loading to go away. It should only go away if all requests have completed though.
In axios I just use interceptors and have a counter. It's pretty simple. I really have no clue how to handle this with RxJS though. My guess would be it needs to do something similar, I just really don't know how to write it.

Answer 1

Build a custom HTTP client that exposes a loading BehaviorSubject. Every time a connection is opened increment the count and decrement the count each time a connection finishes. Have your loading indicator show when the connection count is greater than 0 and hide when it is 0.
class HttpClient {
constructor() {
this.connectionCount$ = new rxjs.BehaviorSubject(0);
this.loading$ = new rxjs.BehaviorSubject(false);
}
incrementConnectionCount() {
this.connectionCount$.next(this.connectionCount$.getValue() + 1);
if (this.connectionCount$.getValue() === 1) {
this.loading$.next(true);
}
}
decrementConnectionCount() {
this.connectionCount$.next(this.connectionCount$.getValue() - 1);
if (this.connectionCount$.getValue() === 0) {
this.loading$.next(false);
}
}
get(url) {
this.incrementConnectionCount();
setTimeout(() => { // Simulate a http call that takes 2 seconds
this.decrementConnectionCount();
}, 2000);
}
// Do the same for the other verbs, put, post, delete etc
}
const httpClient = new HttpClient();
// Anywhere you want a loading spinner subscribe to the loading observable and show and hide the spinner
httpClient.loading$.subscribe(loading => {
document.getElementById('loading').style.display = loading ? 'block' : 'none';
});
// Show the connection count
httpClient.connectionCount$.subscribe(connectionCount => {
document.getElementById('connectionCount').innerText = connectionCount;
});
// Each time you click the button you will simulate a http get that takes two seconds, press it multople times and it will show for 2 seconds after the last click
document.getElementById('load').addEventListener('click', () => {
httpClient.get('someUrl');
});
#loading {
display: none;
}
svg {
vertical-align: middle;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/6.3.3/rxjs.umd.min.js"></script>
<button id="load">Load</button> Connection count: <span id="connectionCount"></span>
<div id="loading"> <!-- Get a funky loading spinner from loading.io -->
<svg xmlns="http://www.w3.org/2000/svg" class="lds-cutiefox" width="80px" height="80px" viewBox="0 0 100 100" preserveAspectRatio="xMidYMid">
<g transform="rotate(80.5368 50 50)">
<animateTransform attributeName="transform" type="rotate" values="360 50 50;0 50 50" keyTimes="0;1" dur="1.5s" repeatCount="indefinite" calcMode="spline" keySplines="0.5 0 0.5 1" begin="-0.15000000000000002s"/>
<circle cx="50" cy="50" r="39.891" stroke="#ffc254" stroke-width="14.4" fill="none" stroke-dasharray="0 300">
<animate attributeName="stroke-dasharray" values="15 300;55.1413599195142 300;15 300" keyTimes="0;0.5;1" dur="1.5s" repeatCount="indefinite" calcMode="linear" keySplines="0 0.4 0.6 1;0.4 0 1 0.6" begin="-0.069s"/>
</circle>
<circle cx="50" cy="50" r="39.891" stroke="#fff1cf" stroke-width="7.2" fill="none" stroke-dasharray="0 300">
<animate attributeName="stroke-dasharray" values="15 300;55.1413599195142 300;15 300" keyTimes="0;0.5;1" dur="1.5s" repeatCount="indefinite" calcMode="linear" keySplines="0 0.4 0.6 1;0.4 0 1 0.6" begin="-0.069s"/>
</circle>
<circle cx="50" cy="50" r="32.771" stroke="#000000" stroke-width="1" fill="none" stroke-dasharray="0 300">
<animate attributeName="stroke-dasharray" values="15 300;45.299378454348094 300;15 300" keyTimes="0;0.5;1" dur="1.5s" repeatCount="indefinite" calcMode="linear" keySplines="0 0.4 0.6 1;0.4 0 1 0.6" begin="-0.069s"/>
</circle>
<circle cx="50" cy="50" r="47.171" stroke="#000000" stroke-width="1" fill="none" stroke-dasharray="0 300">
<animate attributeName="stroke-dasharray" values="15 300;66.03388996804073 300;15 300" keyTimes="0;0.5;1" dur="1.5s" repeatCount="indefinite" calcMode="linear" keySplines="0 0.4 0.6 1;0.4 0 1 0.6" begin="-0.069s"/>
</circle>
</g>
<g transform="rotate(143.103 50 50)">
<animateTransform attributeName="transform" type="rotate" values="360 50 50;0 50 50" keyTimes="0;1" dur="1.5s" repeatCount="indefinite" calcMode="spline" keySplines="0.5 0 0.5 1"/>
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