使用 Javascript（无 jquery）从 2 个 json 字符串追加数据 - 追加不是函数

Question

I have formdata i stringify that looks like this

{"name":"jack miller", "address":"123 main st"} 

I want to append more records but i was getting "append is not a function"

goal to have this {"name":"jack miller", "address":"123 main st"}, {"name":"new guy", "address":"new address"}

const s = this hold master data
const data = new FormData(e.target);
let m = JSON.stringify(Object.fromEntries(data));

let c = s.concat(m)  // concat doesn't include a comma 
let d = s.append(m)  // append throw error of  append is not a function

So while i tend to have json strings, i could convert to object or array and then back if that is better or easier to append etc..

Why doesn't append work?

Update: There is jsfiddle of the formdata https://jsfiddle.net/fx6ebaj5

That "m" is what i need to add data to.

Answer 1

How to add objects to array

let arr = [{"name":"jack miller", "address":"123 main st"} 
];

without modifying actual array

let obj = {"name":"John", "address":"432 main st"} 
let newArr = [...arr, obj];
console.log(newArr);

let appendArr=arr.concat(obj)
console.log(appendArr);

modified actual array

arr.push(obj)
console.log(arr)

Answer 2

There are two ways of copying an object in Javascript. One is shallow copying and another one is deep copying. The best way to copy an object would be to deep copy the feature as it would not affect the changes made to the copied one.

JSON.stringify turns an object into a string. JSON.parse turns a string into an object.

Combining them can turn an object into a string, and then reverse the process to create a brand new data structure.

nestedObject = [
 {"name":"jack miller", "address":"123 main st"},
 {"name":"jon", "address":"13 main st"}];

numbersCopy = JSON.parse(
JSON.stringify(nestedNumbers)
);

numbersCopy.push({"name":"Shawn", "address":"13 main st"});
console.log(nestedObject, numbersCopy);

[
 {"name":"jack miller", "address":"123 main st"},
 {"name":"jon", "address":"13 main st"}
];

[
 {"name":"jack miller", "address":"123 main st"},
 {"name":"jon", "address":"13 main st"},
 {"name":"Shawn", "address":"13 main st"}
];

// These two arrays are completely separate!

So in your case to convert m as per your requirement, I would do below steps

const m = {hello: "hello", hi: "hi"}
let mArray = []

for (let [key, value] of Object.entries(m)) {
  let obj = {}
  obj.key = value
  mArray.push(obj)
}

mArray.push({"name":"Shawn", "address":"13 main st"})

So I am converting your m object to an array. It should work now.