packages/node_modules/pouchdb-utils/src/jsExtend.js

// forked from
// https://github.com/vmattos/js-extend/blob/7023fd69a9e9552688086b8b8006b1fcf916a306/extend.js
// TODO: I don't know why we have two different extend() functions in PouchDB

var slice = Array.prototype.slice;
var each = Array.prototype.forEach;

function extend(obj) {
  if (typeof obj !== 'object') {
    throw obj + ' is not an object' ;
  }

  var sources = slice.call(arguments, 1);

  each.call(sources, function (source) {
    if (source) {
      for (var prop in source) {
        if (typeof source[prop] === 'object' && obj[prop]) {
          extend.call(obj, obj[prop], source[prop]);
        } else {
          obj[prop] = source[prop];
        }
      }
    }
  });

  return obj;
}

export default extend;