function deepExtend(target) {
  const sources = Array.prototype.slice.call(arguments, 1);
  sources.forEach(function (source) {
    for (const prop in source) {
      if (!source.hasOwnProperty(prop)) {
        continue;
      }
      const targetProp = target[prop];
      const targetType = (typeof targetProp);
      //target prop is
      // a native single type
      // or not existent
      // or is not an anonymous object (not class instance)
      if (!targetProp ||
        targetType === 'number' ||
        targetType === 'string' ||
        util.isArray(targetProp) ||
        util.isDate(targetProp) ||
        targetProp.constructor.name !== 'Object') {
        target[prop] = source[prop];
      }
      else {
        //inner extend
        target[prop] = deepExtend({}, targetProp, source[prop]);
      }
    }
  });
  return target;
}
function deepExtend(target) {
  const sources = Array.prototype.slice.call(arguments, 1);
  sources.forEach(function (source) {
    for (const prop in source) {
      if (!source.hasOwnProperty(prop)) {
        continue;
      }
      const targetProp = target[prop];
      const targetType = (typeof targetProp);
      //target prop is
      // a native single type
      // or not existent
      // or is not an anonymous object (not class instance)
      if (!targetProp ||
        targetType === 'number' ||
        targetType === 'string' ||
        util.isArray(targetProp) ||
        util.isDate(targetProp) ||
        targetProp.constructor.name !== 'Object') {
        target[prop] = source[prop];
      }
      else {
        //inner extend
        target[prop] = deepExtend({}, targetProp, source[prop]);
      }
    }
  });
  return target;
}
function deepExtend ( target ) { const sources = Array . prototype . slice . call ( arguments , 1 ) ; sources . forEach ( function ( source ) { for ( const prop in source ) { if ( ! source . hasOwnProperty ( prop ) ) { continue ; } const targetProp = target [ prop ] ; const targetType = ( typeof targetProp ) ; //target prop is // a native single type // or not existent // or is not an anonymous object (not class instance) if ( ! targetProp || targetType === 'number' || targetType === 'string' || util . isArray ( targetProp ) || util . isDate ( targetProp ) || targetProp . constructor . name !== 'Object' ) { target [ prop ] = source [ prop ] ; } else { //inner extend target [ prop ] = deepExtend ( { } , targetProp , source [ prop ] ) ; } } } ) ; return target ; }
Extends the target by the most inner props of sources
@param {Object} target
@returns {Object}
Extends the target by the most inner props of sources