toValue(str, measurement, popperOffsets, referenceOffsets) {\n // separate value from unit\n const split = str.match(/((?:\\-|\\+)?\\d*\\.?\\d*)(.*)/);\n const value = +split[1];\n const unit = split[2];\n\n // If it's not a number it's an operator, I guess\n if (!value) {\n return str;\n }\n\n if (unit.indexOf('%') === 0) {\n let element;\n switch (unit) {\n case '%p':\n element = popperOffsets;\n break;\n case '%':\n case '%r':\n default:\n element...