JS Built-ins
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ArrayArray.prototype.filterintermediate

Array.prototype.filter() — remove falsy values

📖 Usage Example
const mixed = [0, 1, '', 'hello', null, true]
mixed.filter(Boolean)  // → [1, 'hello', true]

Pass Boolean as the callback to filter() to remove all falsy values in one step.

Array.prototype.filter() — compact

A common utility pattern is to remove all falsy values (false, null, undefined, 0, "", NaN) from an array by passing Boolean as the filter callback.

Challenge: Implement compact(arr) that removes all falsy values from the array.

compact([0, 1, false, 2, '', 3, null]) // → [1, 2, 3]
compact([null, undefined, NaN])        // → []
💡 Hints (2)
  • • `Boolean` as a callback is equivalent to `x => !!x` — it converts each element to boolean.
  • • Falsy values in JS: `false`, `0`, `""`, `null`, `undefined`, `NaN`.