How Can I Merge Two JavaScript Objects?

How to Merge Properties of Two JavaScript Objects

JavaScript does not provide a native method for merging objects directly. However, there are several ways to accomplish this task.

ECMAScript 2018 Standard Method

For ES2018 and later, the object spread syntax allows you to merge objects using the following code:

let merged = {...obj1, ...obj2};

Properties in obj2 will overwrite those in obj1. You can merge multiple objects using the same syntax.

ECMAScript 2015 (ES6) Standard Method

ES6 provides the Object.assign() method to merge objects. The first argument is the target object, while subsequent arguments are objects whose properties will be copied into the target:

Object.assign(obj1, obj2);

// Merge multiple objects
const allRules = Object.assign({}, obj1, obj2, obj3);

Method for ES5 and Earlier

For ES5 and earlier, you can use the following loop to merge objects:

for (var attrname in obj2) { obj1[attrname] = obj2[attrname]; }

This will simply add all attributes of obj2 to obj1, potentially overwriting existing properties.

Additional Notes

• Object.assign() merges objects by reference, while the spread syntax creates a new object.
• If you need more control over the merging process, you can create custom functions for this purpose.

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