JS what situations can't use json Parse, json.stringify deep copy and a better deep copy method

Let's start with one js Concept —>
Object serialization ： Is to change the state of an object into a string （JSON.stringify）, You can also restore strings to objects （JSON.parse）.

We usually use this method to Copy one js object , But in some cases , There will be problems. , For example, in the following cases .

• Among objects NaN、Infinity and -Infinity When , After serialization, it will become null.

• Among objects undefined and Function When it comes to type data , After serialization, it will be lost directly .

• When there is a time type in the object , After serialization, it becomes a string type .

• When an object is referenced circularly , Errors will be reported directly after serialization .

const obj = {
    
    nan:NaN,
    infinityMax:1.7976931348623157E+10308,
    infinityMin:-1.7976931348623157E+10308,
    undef: undefined,
    fun: () => {
     console.log(123) },
    date:new Date,
    name:' Zhang San ',
    wife:obj.name
}

It is recommended to use recursive method to encapsulate a tool function in the project

//utils.js
//...
const deepCopy= (obj = {
     }) => {
    
        // Empty variable first 
        let newobj = null;

        // Determine whether recursion needs to continue 
        if (typeof (obj) == 'object' && obj !== null) {
    
            newobj = obj instanceof Array ? [] : {
    };
            // Perform the next level of recursive cloning 
            for (var i in obj) {
    
                newobj[i] = deepCopy(obj[i])
            }
            // If the object is not directly assigned 
        } else newobj = obj;
        console.log(newobj)
        return newobj;
    }
   

Use ：

 let person= {
    
        name:'zhangsan',
        age:26,
        wife:{
    
            sheName:'xiaohua',
            sheAge:25
        }
    }
 let newPerson= deepCopy(person)