Count the occurrences of a value in an array

Use Array.prototype.reduce() to increment a counter each time the specific value is encountered inside the array.

const countOccurrences = (arr, val) =>
  arr.reduce((a, v) => (v === val ? a + 1 : a), 0);

// EXAMPLE
countOccurrences([1, 1, 2, 1, 2, 3], 1); // 3

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