When attempting to chain Observable.interval() with .flatMap(), I encountered what seems to be unexpected behavior.
Below is the code snippet I am using (with Angular 2):
Observable.interval(1500)
.scan((numArr:any[], curr:any, i:number) => {
numArr.push(i);
return numArr;
}, [])
.do(arr => console.log('interval value', arr))
.flatMap(numArr => {
return Observable.interval(500)
.map(i => {
numArr.forEach((el, i, arr) => {
arr[i] += 1;
})
return numArr;
})
}).subscribe(res => console.log('final value', res));
The current output I am receiving:
interval value [0]
final value [1]
final value [2]
interval value [2, 1]
final value [3, 2]
final value [4, 3]
final value [5, 4]
final value [6, 5]
final value [7, 6]
interval value [7, 6, 2]
final value [8, 7, 3]
final value [9, 8, 4]
final value [10, 9, 5]
....
I expect to receive 3 values between each "interval value" cycle instead of getting a larger list every time the interval emits a value. Why is this happening and how can it be resolved?
My goal is to increment by 1 for each value in the array emitted by the first Observable.interval() every 500ms. Essentially, the desired result is:
interval value [0]
final value [1]
final value [2]
final value [3]
interval value [3, 1]
final value [4, 2]
final value [5, 3]
final value [6, 4]
interval value [6, 4, 1]
final value [7, 5, 2]
final value [8, 6, 3]
final value [9, 7, 4]
....
Any assistance would be greatly appreciated. Thank you.