Array : Parsing object in dart (Unsupported operation: Cannot add to a fixed-length list)

Array : Parsing object in dart (Unsupported operation: Cannot add to a fixed-length list)
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This is a YouTube's feature which works on Desktop.
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You will see a flashing rainbow instead of a regular progress bar on YouTube.

A brief introduction of myself,
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Array : Parsing object in dart (Unsupported operation: Cannot add to a fixed-length list)
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: to list) Parsing dart Cannot fixed-length operation: add (Unsupported Array object a in