Within my code, I encountered a peculiar issue involving a splice line along with debug lines on both sides. Take a look:
const obj = { x:[1,2], y:{t:"!!!"} }
const lenBefore = S.groupings.length
const ret = S.groupings.splice(gix, 0, obj)
console.log(`${lenBefore} --> ${S.groupings.length}, gix=${gix}, ret=${JSON.stringify(ret)}`)
The output produced seemed impossible to me:
3 --> 3, gix=2, ret=[]
This indicated that the splice function did not perform any addition or removal of elements.
A different run using varying data yielded the following result:
18 --> 18, gix=2, ret=[]
Although the function involved is quite complex, I have conducted unit tests covering its primary use cases. When running these tests alongside the console.log() lines, the expected results were obtained:
1 --> 2, gix=0, ret=[]
3 --> 4, gix=1, ret=[]
These results aligned with my expectations. Hence, it appears that certain environmental factors during real-time execution are causing this anomaly.
In my case, which involves an Electron app operating in the front-end (effectively Chrome), the behavior observed differs when compared to unit testing done with Mocha 3.2.0 and Node 6.11.4. Despite confirming via console logs that the type of S.groupings remains consistent across live and test environments, I noticed unexpected mutation behaviors manifesting solely during live executions.
An interesting observation made was that substituting the offending line with another snippet delivered successful outcomes – both in live applications and unit tests:
S.groupings = S.groupings.slice(0,gix).concat(obj, S.groupings.slice(gix))
Evidently, there exists some peculiarity within S.groupings hindering its mutability, particularly within intricate live scenarios but not evident in controlled unit tests. This contradicts the general notion that JavaScript objects are entirely mutable entities.
Further investigations revealed no freezing or sealing components evidently affecting S.groupings:
Object.isFrozen(S.groupings) //false
Object.isSealed(S.groupings) //false
Object.isExtensible(S.groupings) //true
To delve into this inquiry further, I devised three progressively complex simplifications simulating genuine code snippets as Mocha tests, all of which executed successfully without anomalies. The intricacies exhibited by the actual implementation transcend the simplified versions posted above, hinting at potential external nuances contributing to the irregular behavior observed.
// Simplified test examples go here