melt/dist/utils/merge.js

The next generation of Melt UI. Built for Svelte 5.

function isPlainObject(value) {
    return (value !== null && typeof value === "object" && Object.getPrototypeOf(value) === Object.prototype);
}
export function deepMerge(target, source) {
    const result = { ...target };
    for (const key in source) {
        if (Object.prototype.hasOwnProperty.call(source, key)) {
            const sourceValue = source[key];
            const targetValue = result[key];
            // Handle arrays - merge them
            if (Array.isArray(sourceValue)) {
                result[key] = Array.isArray(targetValue)
                    ? [...targetValue, ...sourceValue]
                    : [...sourceValue];
                continue;
            }
            // Handle plain objects (not null, not arrays, not class instances)
            if (isPlainObject(sourceValue)) {
                result[key] =
                    Object.prototype.hasOwnProperty.call(result, key) && isPlainObject(result[key])
                        ? deepMerge(result[key], sourceValue)
                        : deepMerge({}, sourceValue);
                continue;
            }
            // Handle primitives and everything else
            result[key] = sourceValue;
        }
    }
    return result;
}