=> {\n    // Most of the units rely on the orientation of the popper\n    const measurement = (index === 1 ? !useHeight : useHeight)\n      ? 'height'\n      : 'width';\n    let mergeWithPrevious = false;\n    return (\n      op\n        // This aggregates any `+` or `-` sign that aren't considered operators\n        // e.g.: 10 + +5 => [10, +, +5]\n        .reduce((a, b) => {\n          if (a[a.length - 1] === '' && ['+', '-'].indexOf(b) !== -1) {\n            a[a.length - 1] = b;\n            mergeWithPrevious...