CODEWITHSUNDEEP
node.jsnode-promisify
ma1234
ma1234

Reputation: 651

How does promisify know which variable to return?

I used util.promisify on this sqlite3 function:

// Before
db.each("Select * from example;", (error, row) => console.table(row));
db.each = util.promisify(db.each);
// After
async function getRow()
     try {
        console.table(await db.each("Select * from example;")); // line 7
     } catch (e) {
        console.error(e.message);
     }
}

My question is, how does promisify know which variable (the "err" or the "row") to return in line 7?

Upvotes: 1

Views: 284

Answers (1)

Rupjyoti
Rupjyoti

Reputation: 399

The util.promisify() is used/able to convert a callback into promise only if the first parameter of the callback function is the error parameter.

So, it will always return "row" in Line 7. If there is an error, it will go to the catch block.

Upvotes: 1

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