[].concat is not a function

[tomduncalf]

Getting this if I trigger loads of notes in my application. Not sure if it's app specific. I suspect the stack trace does not tell the full story.

index.js:1543 Uncaught TypeError: [].concat is not a function
    at eval (webpack:///./~/mpe/lib/index.js?:1543:23)
    at Array.forEach (native)
    at activeNotes (webpack:///./~/mpe/lib/index.js?:1542:22)
    at combination (webpack:///./~/mpe/lib/index.js?:880:30)
    at dispatch (webpack:///./~/mpe/lib/index.js?:478:23)
    at Array.forEach (native)
    at Object.processMidiMessage (webpack:///./~/mpe/lib/index.js?:168:14)
    at MIDIInput.input.onmidimessage (webpack:///./src/midi/handleInput.ts?:55:40)

The code in question:

[odub]

Could this be TypeScript related? I some issues over on their project about the type signature for [].concat. The only other possibilities I see are: some other code overriding the Array prototype, or that the error message is just misleading.

[tomduncalf]

Type signatures don't affect anything at runtime, they're just used for checking at compile time. It could be Typescript doing some dodgy transpilation although generally it is quite light on the transpilation. Could be a Babel thing. Could be magic. Not to worry!

On 8 February 2017 at 12:59, Oscar Dub [email protected] wrote:

Could this be TypeScript related? I some issues over on their project about the type signature for [].concat. The only other possibilities I see are: some other code overriding the Array prototype, or that the error message is just misleading.

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