Lodash's cloneDeep() Function

You can use lodash's cloneDeep() function to deep copy a value.

const _ = require('lodash');

const obj = [{ a: 1, b: 2 }];

const copy = _.cloneDeep(obj);
console.log(copy); // [{ a: 1, b: 2 }];

With Classes

If you call cloneDeep() on an instance of a class, cloneDeep() will also copy the class information.

class MyClass {};
const obj  = new MyClass();

const copy = _.cloneDeep(obj);
copy instanceof MyClass; // true

Warning: Proxies

cloneDeep() does not work well with Mongoose documents or reactive objects in Vue. With Vue, the cloned object will not be reactive. With Mongoose documents, you won't be able to save the cloned document.

const _ = require('lodash');
const mongoose = require('mongoose');
async function run() {
  await mongoose.connect('mongodb://localhost:27017/test5');

  const arr2Schema = new mongoose.Schema({ _id: false, prop1: String });
  const arr1Schema = new mongoose.Schema({ _id: false, arr2: [arr2Schema] });
  const Test = mongoose.model(
    'Test',
    new mongoose.Schema({
      arr1: [arr1Schema],
      field: String,
    }),
  );

  let doc = new Test({ arr1: [{ arr2: [{ prop1: 'test' }] }] });
  await doc.save();

  const doc2 = await Test.findById(doc._id);
  const newDoc = _.cloneDeep(doc2).set({ field: 'test' });

  await newDoc.save(); // Mongoose-internal TypeError
}

run();

In general, we only recommend using cloneDeep() on POJOs.

More Lodash Tutorials

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