callback hell

callback hell (uncountable)

(programming, colloquial) (mostly of the JavaScript language) The situation where callbacks are nested within other callbacks several levels deep, potentially making it difficult to understand and maintain the code.
- 2015, Remo H. Jansen, Learning TypeScript‎:
  However, the use of callbacks can lead to a maintainability issue known as callback hell. We will now write a real-life example to showcase what a callback hell is and how easily we can end up dealing with it.

situation where callbacks are nested within other callbacks

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