Using Array.prototype.map in conjunction with parseInt functions

Recently, I encountered something quite unusual.

I am attempting to separate a string containing a time (e.g. "12:00", "13:30") into two distinct integers. I experimented with the following approach:

timeString = "12:00"
[hours, minutes] = timeString.split(":").map(parseInt)

However, the output for minutes turns out to be NaN.

Initially, I suspected that parseInt was causing an issue when processing "00", but upon testing parseInt("00") in the console, it resulted in 0.

Could someone provide some clarification on this matter?

javascriptarrays

Answer №1

Array#map executes the function with three parameters:

  1. The current item

  2. The current position

  3. The array itself

In this code snippet, parseInt is invoked with "00" and 1 (which represents the index):

timeString = "12:00"
[hours, minutes] = timeString.split(":").map(parseInt)

The second argument for parseInt must be greater than 2 to prevent returning NaN.

This is the issue illustrated here.

To address this, you can use:

timeString = "12:00"
[hours, minutes] = timeString.split(":").map(v => parseInt(v, 10))

Answer №2

When using parseInt, make sure to provide two arguments: parseInt(value, base). This method can handle various number systems like binary and hexadecimal. Similarly, the .map function takes a callback with parameters .map(item, index).

To fix the issue of returning NaN when calling parseInt("00", 1), update your code as follows: 


timeString = "12:00"
var [hours, minutes] = timeString.split(":").map(i => parseInt(i))

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