js determines value based on key

 The most original way of writing:

Improved writing: 

 const DeviceTypeObj = {
                        SO2: "SO<sub>2</sub>",
                        CO: "CO",
                        NO: "NO",
                        NO2: "NO<sub>2</sub>",
                        O3: "O<sub>3</sub>",
let value = DeviceTypeObj[DeviceType] ?? DeviceType; //??是javascript中的控制合并运算符，作用是用于处理变量或表达式的空值或未定义的情况。