What's the best way to convert values to/from a range of 0-99 and 0-100?

For example, Homebridge MQTT-Thing (using Node.js and JavaScript) only supports values of 0-100. However, my zwavejs2mqtt devices only support 0-99.

What's the best way to convert values to/from both of these systems using JavaScript? (ie. MQTT-Thing supports custom JavaScript functions to encode/decode messages where I can convert the values)