manual code idea

manual.js

const manuals=[
  {
    "type":"switch",
    "subtypes":[
      {
        "description": "container including a switch going to u8, u16 or u32",
        "encoder":(value,buffer,offset) => {
          const {action,result}=value;
          offset+=buffer.writeUInt8(action,offset);
          switch(action) {
            case 0:
              offset+=buffer.writeUInt8(result,offset);
              break;

            case 1:
              offset+=buffer.writeUInt16BE(result,offset);
              break;

            case 2:
              offset+=buffer.writeUInt32BE(result,offset);
              break;
          }
          return offset;
        },
        "decoder":(buffer,offset) => {
          const action=buffer.readUInt8(offset);
          offset+=1;
          let result;
          switch(action) {
            case 0:
              result=buffer.readUInt8(offset);
              offset+=1;
              break;

            case 1:
              result=buffer.readUInt16BE(offset);
              offset+=2;
              break;

            case 2:
              result=buffer.readUInt32BE(offset);
              offset+=4;
              break;
          }
          const value={action,result};
          return {value,offset};
        },
        "type": ["container",
          [
            {
              "name":"action",
              "type":"u8"
            },
            {
              "name":"result",
              "type":["switch",
                {
                  "compareTo":"action",
                  "fields":{
                    "0":"u8",
                    "1":"u16",
                    "2":"u32"
                  }
                }
              ]
            }
          ]
        ],
        "values":[
          {
            "description":"u8",
            "value":{
              "action":0,
              "result":3
            },
            "buffer":["0x00","0x03"]
          },
          {
            "description":"u32",
            "value":{
              "action":2,
              "result":4294966272
            },
            "buffer":["0x02","0xff","0xff","0xfc","0x00"]
          }
        ]
      }
    ]
  }
];


function arrayToBuffer(arr)
{
  return new Buffer(arr.map(e => parseInt(e)));
}

function transformValues(type,values)
{
  return values.map(value => ({
    buffer: arrayToBuffer(value.buffer),
    value: type.indexOf("buffer") == 0 ? arrayToBuffer(value.value) : value.value,
    description: value.description
  }));
}

console.log(manuals[0]["subtypes"][0]["decoder"](transformValues(manuals[0]["type"],manuals[0]["subtypes"][0]["values"])[0]["buffer"],0));