duplicate_product_graphql.js

const req_query = 
mutation productDuplicate($productId: ID!, $newTitle: String!) {
  productDuplicate(productId: $productId, newTitle: $newTitle) {
    userErrors {
      field
      message
    }
    imageJob {
      id
    }
    newProduct {
      id
    }
    shop {
      id
    }
  }
}

duplicate_product_rest.js

axios.get(`/admin/product/id.json`).then(function(productResponse){
  let newProductBody = productResponse.product;
  newProductBody.title = "My New Title";
  axios.post(`/admin/product.json, newProductBody).then(function(productCreateResponse) {
    
  });
});