joint.all.js
function baseClone(value, deep, callback, stackA, stackB) {
      if (callback) {
        var result = callback(value);
        if (typeof result != 'undefined') {
          return result;
        }
      }
      // inspect [[Class]]
      var isObj = isObject(value);
      if (isObj) {
        var className = toString.call(value);
        if (!cloneableClasses[className]) {
          return value;
        }
        var ctor = ctorByClass[className];
        switch (className) {
          case boolClass:
          case dateClass:
            return new ctor(+value);

          case numberClass:
          case stringClass:
            return new ctor(value);

          case regexpClass:
            result = ctor(value.source, reFlags.exec(value));
            result.lastIndex = value.lastIndex;
            return result;
        }
      } else {
        return value;
      }
      var isArr = isArray(value);
      if (deep) {
        // check for circular references and return corresponding clone
        var initedStack = !stackA;
        stackA || (stackA = getArray());
        stackB || (stackB = getArray());

        var length = stackA.length;
        while (length--) {
          if (stackA[length] == value) {
            return stackB[length];
          }
        }
        result = isArr ? ctor(value.length) : {};
      }
      else {
        result = isArr ? slice(value) : assign({}, value);
      }
      // add array properties assigned by `RegExp#exec`
      if (isArr) {
        if (hasOwnProperty.call(value, 'index')) {
          result.index = value.index;
        }
        if (hasOwnProperty.call(value, 'input')) {
          result.input = value.input;
        }
      }
      // exit for shallow clone
      if (!deep) {
        return result;
      }
      // add the source value to the stack of traversed objects
      // and associate it with its clone
      stackA.push(value);
      stackB.push(result);

      // recursively populate clone (susceptible to call stack limits)
      (isArr ? forEach : forOwn)(value, function(objValue, key) {
        result[key] = baseClone(objValue, deep, callback, stackA, stackB);
      });

      if (initedStack) {
        releaseArray(stackA);
        releaseArray(stackB);
      }
      return result;
    }
function baseClone(value, deep, callback, stackA, stackB) {
      if (callback) {
        var result = callback(value);
        if (typeof result != 'undefined') {
          return result;
        }
      }
      // inspect [[Class]]
      var isObj = isObject(value);
      if (isObj) {
        var className = toString.call(value);
        if (!cloneableClasses[className]) {
          return value;
        }
        var ctor = ctorByClass[className];
        switch (className) {
          case boolClass:
          case dateClass:
            return new ctor(+value);

          case numberClass:
          case stringClass:
            return new ctor(value);

          case regexpClass:
            result = ctor(value.source, reFlags.exec(value));
            result.lastIndex = value.lastIndex;
            return result;
        }
      } else {
        return value;
      }
      var isArr = isArray(value);
      if (deep) {
        // check for circular references and return corresponding clone
        var initedStack = !stackA;
        stackA || (stackA = getArray());
        stackB || (stackB = getArray());

        var length = stackA.length;
        while (length--) {
          if (stackA[length] == value) {
            return stackB[length];
          }
        }
        result = isArr ? ctor(value.length) : {};
      }
      else {
        result = isArr ? slice(value) : assign({}, value);
      }
      // add array properties assigned by `RegExp#exec`
      if (isArr) {
        if (hasOwnProperty.call(value, 'index')) {
          result.index = value.index;
        }
        if (hasOwnProperty.call(value, 'input')) {
          result.input = value.input;
        }
      }
      // exit for shallow clone
      if (!deep) {
        return result;
      }
      // add the source value to the stack of traversed objects
      // and associate it with its clone
      stackA.push(value);
      stackB.push(result);

      // recursively populate clone (susceptible to call stack limits)
      (isArr ? forEach : forOwn)(value, function(objValue, key) {
        result[key] = baseClone(objValue, deep, callback, stackA, stackB);
      });

      if (initedStack) {
        releaseArray(stackA);
        releaseArray(stackB);
      }
      return result;
    }
/*-------------------------------------------------------------------------- 
The base implementation of `_.clone` without argument juggling or support
for `thisArg` binding.

@private
@param {*} value The value to clone.
@param {boolean} [deep=false] Specify a deep clone.
@param {Function} [callback] The function to customize cloning values.
@param {Array} [stackA=[]] Tracks traversed source objects.
@param {Array} [stackB=[]] Associates clones with source counterparts.
@returns {*} Returns the cloned value.