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

You can use arrow function ES2015/ES6 and just pass number to the parseInt. Default value for radix will be 10

[10, 20, 30].map(x => parseInt(x))

Or you can explicitly specify radix for better readability of your code.

[10, 20, 30].map(x => parseInt(x, 10))

In example above radix explicitly set to 10