How Do I Merge JavaScript Objects Effectively?

Merging JavaScript Objects

Introduction:

Combining data from multiple sources is a common task in JavaScript development. Merging objects is a technique that allows you to combine properties from different objects into a single entity. This article explores different methods for merging JavaScript objects.

Built-in Merge Methods in Modern JavaScript

Object Spread Syntax (ES2018):

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

Object.assign (ES2015):

Object.assign(obj1, obj2);

These methods merge the properties of obj2 into obj1. Properties in obj2 will overwrite any existing properties with the same name in obj1.

Merging Objects in Older JavaScript Versions (ES5 and Earlier)

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

This method copies all properties from obj2 to obj1, including those that already exist in obj1.

Custom Merge Function for Handling Conflicts

If you need more control over merging behavior, you can create a custom function:

function merge_options(obj1, obj2) {
    var obj3 = {};
    for (var attrname in obj1) { obj3[attrname] = obj1[attrname]; }
    for (var attrname in obj2) { obj3[attrname] = obj2[attrname]; }
    return obj3;
}

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