Function merge

src/helpers/helpers.core.ts:260–285

(target: T, source: AnyObject[], options?: MergeOptions)

): T & S1 & S2 & S3 & S4;
export function merge<T>(target: T, source: AnyObject[], options?: MergeOptions): AnyObject;
export function merge<T>(target: T, source: AnyObject[], options?: MergeOptions): AnyObject {
  const sources = isArray(source) ? source : [source];
  const ilen = sources.length;

  if (!isObject(target)) {
    return target as AnyObject;
  }

  options = options || {};
  const merger = options.merger || _merger;
  let current: AnyObject;

  for (let i = 0; i < ilen; ++i) {
    current = sources[i];
    if (!isObject(current)) {
      continue;
    }

    const keys = Object.keys(current);
    for (let k = 0, klen = keys.length; k < klen; ++k) {
      merger(keys[k], target, current, options as AnyObject);
    }
  }

  return target;
}

/**
 * Recursively deep copies `source` properties into `target` *only* if not defined in target.