Splice method gives error.

In the below code I am trying to remove the element from the array, the splice method is failing for some reason.
// this.productId =  {
    //     [
    //         {
    //             "Id": "a001700000802ZJAAY",
    //             "Name": "Medium Pizza",
    //             "Price__c": 9
    //         },
    //         {
    //             "Id": "a0017000007ztMUAAY",
    //             "Name": "Large Pizza",
    //             "Price__c": 10
    //         }
    //     ]
    // }

    handleDeleteSelected(event){
        console.log('handle Delete', JSON.stringify(event.detail))
    //    handle Delete {"Id":"a001700000802ZJAAY","Name":"Medium Pizza","Price__c":9}
        var del = event.detail.Id
        const productIndex = this.productId.findIndex(e => e.Id === del);
         const productupdate = this.productId;
  // delete the Medium Pizza from the productupdate array
        productupdate.splice(productIndex, 1)

      console.log('productIndex', productIndex)

      console.log(productupdate)
    }