TypeError: this.findOne is not a function

Question

I am trying to get user data from mongodb using get method but it continuously giving me the error that user.findOne is not a function user token and id get successfully but findOne is not working, I used static methods with user Schema. Please help me in this regard. thank you.

Here is the Code:

//userController.js

Router.get("/user",(req,res,next)=>{

    var token=req.header("x-auth");
    console.log("token3: "+token);
    console.log(User);

    User.findUserByToken(token).then((then)=>{
        if(!User){
            Promise.reject();
        }else{
            req.user=user;
            req.token=token;
            next();
        }
    }).catch((error)=>{
        res.status(401).send();
    });
},(req,res)=>{
    res.send(req.user).then(()=>{

    }).catch(()=>{

    });
})

//user.js 

const Schema=mongoose.Schema;
const userSchema=new Schema({
    name:{
        type: String,
        trim: true,
        required: true,
        minlength: 6
    },
    email:{
        type:String,
        unique:true,
        trim: true,
        required: true,
        minlength: 6
    },
    password:{
        type: String,
        trim: true,
        required: true,
        minlength: 8
    },
    tokens:[
        {
            access:{
                type:String,
                required:true
            },
            token:{
                type:String,
                required:true
            }
        }
    ]
});


userSchema.statics.findUserByToken=(token)=>{
    const User= this;

    console.log(User);
    let decoded;
    try{

        decoded=jwt.verify(token,"asdfghjkl");
    }catch(e){

        return Promise.reject();
    }
    this.findOne({
        "_id":decoded._id,
        "tokens.token":token,                                                                         
        "tokens.access":"auth"
    }).then((data)=>{
        return data;
    })
}   

const User=mongoose.model('users',userSchema);

module.exports={User}        

here is Error in Postman:

TypeError: this.findOne is not a function
    at Function.userSchema.statics.findUserByToken (D:\react-native\reactNativeBackend\models\user.js:123:10)
    at D:\react-native\reactNativeBackend\controllers\userController.js:47:10
    at Layer.handle [as handle_request] (D:\react-native\reactNativeBackend\node_modules\express\lib\router\layer.js:95:5)
    at next (D:\react-native\reactNativeBackend\node_modules\express\lib\router\route.js:137:13)
    at Route.dispatch (D:\react-native\reactNativeBackend\node_modules\express\lib\router\route.js:112:3)
    at Layer.handle [as handle_request] (D:\react-native\reactNativeBackend\node_modules\express\lib\router\layer.js:95:5)
    at D:\react-native\reactNativeBackend\node_modules\express\lib\router\index.js:281:22
    at Function.process_params (D:\react-native\reactNativeBackend\node_modules\express\lib\router\index.js:335:12)
    at next (D:\react-native\reactNativeBackend\node_modules\express\lib\router\index.js:275:10)
    at Function.handle (D:\react-native\reactNativeBackend\node_modules\express\lib\router\index.js:174:3)
    at router (D:\react-native\reactNativeBackend\node_modules\express\lib\router\index.js:47:12)
    at Layer.handle [as handle_request] (D:\react-native\reactNativeBackend\node_modules\express\lib\router\layer.js:95:5)
    at trim_prefix (D:\react-native\reactNativeBackend\node_modules\express\lib\router\index.js:317:13)
    at D:\react-native\reactNativeBackend\node_modules\express\lib\router\index.js:284:7
    at Function.process_params (D:\react-native\reactNativeBackend\node_modules\express\lib\router\index.js:335:12)
    at next (D:\react-native\reactNativeBackend\node_modules\express\lib\router\index.js:275:10)

Answer 1

This was stated in the docs here:

Do not declare statics using ES6 arrow functions (=>). Arrow functions explicitly prevent binding this.

So you need to change the arrow function into a function expression:

userSchema.statics.findUserByToken = function (token) {
  const User = this;

  console.log(User);
  let decoded;
  try {

    decoded = jwt.verify(token, "asdfghjkl");
  } catch (e) {

    return Promise.reject();
  }
  this.findOne({
    "_id": decoded._id,
    "tokens.token": token,
    "tokens.access": "auth"
  }).then((data) => {
    return data;
  })
}