I recently encountered an interesting scenario involving code where I was attempting to connect a subject to an interval observable:
const subject = new Subject();
// Establish the connection between the subject and the observable
interval(1000).subscribe(subject); //**Line 1**
subject.subscribe((value: any) => {
console.log(`Subscriber A: Value: ${value}`);
});
setTimeout(() => {
subject.subscribe((value: any) => {
console.log(`Subscriber B: Value: ${value}`);
});
}, 3000);
The expected output for this setup is as follows:
Subscriber A: Value: 0
Subscriber A: Value: 1
Subscriber A: Value: 2
Subscriber A: Value: 3
Subscriber B: Value: 3
Subscriber A: Value: 4
Subscriber B: Value: 4
Subscriber A: Value: 5
Subscriber B: Value: 5
This output matched my expectations. However, upon modifying the order of connecting the subject and observable, the results varied:
const subject = new Subject();
subject.subscribe((value: any) => {
console.log(`Subscriber A: Value: ${value}`);
});
setTimeout(() => {
subject.subscribe((value: any) => {
console.log(`Subscriber B: Value: ${value}`);
});
}, 3000);
// Connect the subject to the observable
interval(1000).subscribe(subject); //**Line 1**
The resulting output is now:
Subscriber A: Value: 0
Subscriber A: Value: 1
Subscriber A: Value: 2
Subscriber B: Value: 2
Subscriber A: Value: 3
Subscriber B: Value: 3
Subscriber A: Value: 4
Subscriber B: Value: 4
Subscriber A: Value: 5
Subscriber B: Value: 5
This differing outcome raised some questions in my mind.
Why does changing the position of Line 1 lead to differences in output?
In the second output, why does subscriber B begin from value 2 instead of 3 like in the first output, despite both scenarios having a 3-second delay? What fundamental concept might be eluding me here?
After testing both versions of the code, I anticipated the first output but found the discrepancy in the second output perplexing. I am eager to gain insights into the underlying cause behind such behavior.