frankiehayward
10/9/2019 - 2:46 PM

bifurcateBy

This snippet splits values into two groups, based on a predicate function. If the predicate function returns a truthy value, the element will be placed in the first group. Otherwise, it will be placed in the second group. You can use Array.prototype.reduce() and Array.prototype.push() to add elements to groups, based on the value returned by fn for each element.

bifurcate_by.js
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const bifurcateBy = (arr, fn) =>
  arr.reduce((acc, val, i) => (acc[fn(val, i) ? 0 : 1].push(val), acc), [[], []]);
  
bifurcateBy(['beep', 'boop', 'foo', 'bar'], x => x[0] === 'b'); 
// [ ['beep', 'boop', 'bar'], ['foo'] ]