LWC:"ReferenceError: a is not defined at eval (eval at productFamilyOptions

Question

getSettings method below returns settings JSON record and when i am trying to set picklist options using productFamilyOptions variable which is used as options of the .html file, I am getting this error("ReferenceError: a is not defined at eval (eval at productFamilyOptions) in the catch section below. Can someone please help.

<template>

<lightning-combobox name="ProductFamily" label="Product Family" value={Opp.Type__c} placeholder="select product family" options={productFamilyOptions}></lightning-combobox>

</template>

JavaScript

import { LightningElement, track, wire} from 'lwc';
import getSettings from '@salesforce/apex/ContactsUtility.getSettings';

export default class CreateOpportunity extends LightningElement {

@track productFamilyOptions = [];

  connectedCallback() {

    getSettings() .then(result => {   
      for(let key in JSON.parse(result[0].Data__c).family){
        if(key){
        this.productFamilyOptions.push({"label":key,"value":key});
        }
      }

  })
  .catch(error => {
      this.error = error;
  });

}

Answer 1

Replacing this.productFamilyOptions.push({"label":key,"value":key});
with this.productFamilyOptions = [...this.productFamilyOptions,{"label":key,"value":key}];
has resolved my issue. As per my limited knowledge on LWC, push operation doesnot work on arrays with @track. we have to use spread syntax to add elements to array instead of push