underscore.js只支持潜拷贝吗？

var src = {
  src: 'SRC',
  test: {
    name: 'test',
    val: 0
  }
};

var dist1 = _.extend({ dist: 1 }, src);
dist1.test.name = 'test1';
dist1.test.val = 1;
console.log('src', src);
console.log('dest1', dist1);

var dist2 = _.extend({}, src);
dist2.dist = 2;
dist2.test.name = 'test2';
console.log('src', src);
console.log('dest2', dist2);

var dist3 = _.clone(src);
dist3.dist = 3;
console.log('src', src);
console.log('dest3', dist3);

运行这段代码发现，test其实是同一个引用
这样不是一不小心就会产生bug?

---

试试 Lodash，兼容underscore，并且优化了性能，同时对api进行了扩展
里面就有 _.clone() _.cloneDeep()

_.clone(value, [isDeep], [customizer], [thisArg])
_.cloneDeep(value, [customizer], [thisArg])

详见

https://lodash.com/docs#clone
https://lodash.com/docs#cloneDeep