Unexpected Behavior Of Bound Function

Tried to create a function mapping numeric characters (i.e. '0' to '9') to true and other characters to false: const isNumeric = String.prototype.includes.bind('0123456789'); isNu

Solution 1:

includes has a second parameter called position which is the position within the string at which to begin searching. every, like every other array prototype methods, provides the index as the second argument to the callback provided. So, the code ends up being something like this:

const exists = ['1', '0'].every((n, i) =>isNumeric(n, i))

// Which translates to// Look for "1" starting from index 0. It is found// Look for "0" starting from index 1. Fails because "0" is at index 0const exists = ['1', '0'].every((n, i) =>'0123456789'.includes(n, i))

Here's a snippet:

const isNumeric = String.prototype.includes.bind('0123456789'),
      numbers = Array.from('149563278'); // array of numbers in random orderconsole.log( numbers.every(isNumeric) ) // falseconsole.log( numbers.every(n =>isNumeric(n)) ) // true