Syntax error How to add properties from one object into another without overwriting in JavaScript?

How to add properties from one object into another without overwriting in JavaScript?

Let’s say the following are our objects −

var first = {key1: 100, key2: 40, key3: 70}
var second = {key2: 80, key3: 70, key4: 1000}

You can use the concept of hasOwnProperty() to add properties from one object to another. Following is the code −

Example

var first = {key1: 100, key2: 40, key3: 70}
var second = {key2: 80, key3: 70, key4: 1000}
function addPropertiesWithoutOverwritting(first, second) {
   for (var key2 in second) {
      if (second.hasOwnProperty(key2) && !first.hasOwnProperty(key2)) {
         first[key2] = second[key2];
      }
   }
   return first;
}
console.log(addPropertiesWithoutOverwritting(first, second))

To run the above program, you need to use the following command −

node fileName.js.

Output

Here, my file name is demo99.js. This will produce the following output −

PS C:\Users\Amit\JavaScript-code> node demo99.js
{ key1: 100, key2: 40, key3: 70, key4: 1000 }
Updated on: 2020-09-07T08:40:22+05:30

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