当我安慰 console.log 时，我得到了未定义

Question

when i consoled err.kind i got value for it but when i set (error = { ...err };) then i did console i had undefined in my console ?!

      module.exports = (err,req,res,next)=>{
       err.statusCode = err.statusCode || 500 ;
        err.state = err.state ||"error";
        if(process.env.NODE_ENV === "development"){
            console.log(err.name)
        DevError(err,res);
        }
        else if (process.env.NODE_ENV !== "development"){ 
        let error = { ...err };
            if(error.kind === "CastError") error= wrongID(error)
           console.log(error.kind)
        cliError(error,res);
         
        }
    }

Answer 1

This is a rest destructuring issue where only the enumerable properties are getting copied over. Search for "Rest in Object Destructuring" here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment

Consider this:

const example1 = { a: 1 };

// this creates a non-enumerable property "b"
Object.defineProperty(example1, 'b', { value: 2 });

const example2 = { ...example1 };

console.log(example1.a);
// 1
console.log(example1.b);
// 2
console.log(example2.a);
// 1
console.log(example2.b);
// undefined