Why does parseInt yield NaN with Array#map?

Question

From the Mozilla Developer Network:

[1,4,9].map(Math.sqrt)

will yield:

[1,2,3]

Why then does this:

<

Answer 1

parseInt IMHO should be avoided for this very reason. You can wrap it to make it more safe in these contexts like this:

const safe = {
  parseInt: (s, opt) => {
    const { radix = 10 } = opt ? opt : {};
    return parseInt(s, radix);
  }
}

console.log( ['1','2','3'].map(safe.parseInt) );
console.log(
  ['1', '10', '11'].map(e => safe.parseInt(e, { radix: 2 }))
);

lodash/fp caps iteratee arguments to 1 by default to avoid these gotchas. Personally I have found these workarounds to create as many bugs as they avoid. Blacklisting parseInt in favor of a safer implementation is, I think, a better approach.