How can I deep merge two objects in JavaScript?

How can I deep merge two objects in JavaScript?

You can use the Object.assign() method or the spread operator, but for deep merging, a custom function is often needed.

Can you show me a custom function for deep merging?

Sure! Here's a simple example:

function deepMerge(target, source) {
    for (const key in source) {
        if (source[key] instanceof Object) {
            if (!target[key]) Object.assign(target, { [key]: {} });
            deepMerge(target[key], source[key]);
        } else {
            Object.assign(target, { [key]: source[key] });
        }
    }
    return target;
}

What if the objects have arrays?

If the objects contain arrays, you'll need to handle them specifically, as the above function will overwrite them. You can modify the function to concatenate arrays instead.