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Callbacks

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Callbacks

Callbacks is simple if you keep it on paper. Isha uses it for read notes.txt in a script.

Do Callbacks once by hand. (err, data) => …. Change one input. Say the new result out loud.

Callbacks exists so Isha can keep read notes.txt correct in a script.

Isha ships Callbacks in a script. That is the use case worth saying.

Callbacks trap — callback hell, no error-first. Isha loses marks for that every viva.

After Callbacks, Isha should still remember callback hell, no error-first.

Close Callbacks with — “If I skip it, read notes.txt goes wrong like this: callback hell, no error-first.”

Exam tip

Say Callbacks in one breath, then (err, data) => …, then callback hell, no error-first.

Example

// Callbacks
const users = [
  { id: 1, name: "Asha" },
  { id: 2, name: "Ravi" },
];

function findUser(id) {
  return users.find((u) => u.id === id) ?? null;
}

console.log(findUser(2));
console.log(users.map((u) => u.name));

Callbacks: find user 2, then list names. Say both prints.

Short notes

DefCallbacks — Isha uses it for read notes.txt in a script.
RuleCallbacks → (err, data) => ….
RememberCallbacks + an Express route (a script).
UseCallbacks in a script (read notes.txt).
TrapCallbacks — callback hell, no error-first.
ExCallbacks → read notes.txt.

// Callbacks const users = [ { id: 1, name: "Asha" }, { id: 2, name: "Ravi" }, ]; function findUser(id) { return users.find((u) => u.id === id) ?? null; } console.log(findUser(2)); console.log(users.map((u) => u.name));

Callbacks

Example

Short notes

Questions

Callbacks

Example

Short notes

Questions