ts-deepmerge/esm/index.js

A TypeScript deep merge function.

// istanbul ignore next
const isObject = (obj) => {
    if (typeof obj === "object" && obj !== null) {
        if (typeof Object.getPrototypeOf === "function") {
            const prototype = Object.getPrototypeOf(obj);
            return prototype === Object.prototype || prototype === null;
        }
        return Object.prototype.toString.call(obj) === "[object Object]";
    }
    return false;
};
const UNSAFE_KEYS = new Set([
    "__proto__",
    "constructor",
    "prototype",
    "toString",
    "valueOf",
    "hasOwnProperty",
    "isPrototypeOf",
    "propertyIsEnumerable",
    "toLocaleString",
]);
export const merge = (...objects) => objects.reduce((result, current) => {
    if (current === undefined) {
        return result;
    }
    if (Array.isArray(current)) {
        throw new TypeError("Arguments provided to ts-deepmerge must be objects, not arrays.");
    }
    Object.keys(current).forEach((key) => {
        if (UNSAFE_KEYS.has(key)) {
            return;
        }
        if (Array.isArray(result[key]) && Array.isArray(current[key])) {
            result[key] = merge.options.mergeArrays
                ? merge.options.uniqueArrayItems
                    ? Array.from(new Set(result[key].concat(current[key])))
                    : [...result[key], ...current[key]]
                : current[key];
        }
        else if (isObject(result[key]) && isObject(current[key])) {
            result[key] = merge(result[key], current[key]);
        }
        else if (!isObject(result[key]) && isObject(current[key])) {
            result[key] = merge(current[key], undefined);
        }
        else {
            result[key] =
                current[key] === undefined
                    ? merge.options.allowUndefinedOverrides
                        ? current[key]
                        : result[key]
                    : current[key];
        }
    });
    return result;
}, {});
const defaultOptions = {
    allowUndefinedOverrides: true,
    mergeArrays: true,
    uniqueArrayItems: true,
};
merge.options = defaultOptions;
merge.withOptions = (options, ...objects) => {
    merge.options = Object.assign(Object.assign({}, defaultOptions), options);
    const result = merge(...objects);
    merge.options = defaultOptions;
    return result;
};