19. 编写nodejs链码

const shim = require('fabric-shim');
const Chaincode = class{
    //链码初始化操作
    async Init(stub){
        var ret = stub.getFunctionAndParameters();
        var args  = ret.params;
        var a = args[0];
        var aValue = args[1];
        var b = args[2];
        var bValue = args[3];
        await  stub.putState(a,Buffer.from(aValue));
        await  stub.putState(b,Buffer.from(bValue));
        return shim.success(Buffer.from('heima chaincodinit successs'));
    }
 
    async Invoke(stub){
        let ret = stub.getFunctionAndParameters();
        let fcn = this[ret.fcn];
        return fcn(stub,ret.params);
    }
    //查询操作
    async query(stub,args){
        let a = args[0];
        let balance = await stub.getState(a);
        return shim.success(balance);
    }
 
};
shim.start(new Chaincode());