Javascript — How to merge 2 JSON strings together and return a string

Purpose

We will assume that we are starting from two JSON strings and, at the end, we want to obtain a single JSON string with the merged objects.

How to merge 2 JSON objects together

1. We will start our code by defining two JSON strings containing two different objects. These are the objects we will merge.

const string1  = `{
"name": "Todd",
"age": 20
}`;
const string2 = `{
"languages": ["Spanish", "Portuguese"],
"married": true
}`;

2. After defining these JSON strings, we will parse them to JavaScript objects.

const obj1 = JSON.parse(string1);
const obj2 = JSON.parse(string2);

3. We will start by defining a new object with brackets. Then, we will use the spread operator “…” to copy the properties of each original object to the new one.

const mergedObject = {
...obj1,
...obj2
};

Note:

Here in this example, we are doing a shallow copy, so you should be careful to not end up mutating the properties of the original objects, in case they are references to nested…