Kovan Constant

testConstant.js

const ethers = require('ethers');
const provider = ethers.getDefaultProvider('kovan');

const CONTACT_ADDR = "0xae4b4bda19d53178ebbad7737ba34beaa0107c18";
const ABI = [
	{
		"constant": true,
		"inputs": [],
		"name": "activeLength",
		"outputs": [
			{
				"internalType": "uint256",
				"name": "",
				"type": "uint256"
			}
		],
		"payable": false,
		"stateMutability": "view",
		"type": "function"
	}
]

const contract = new ethers.Contract(CONTACT_ADDR, ABI, provider);

contract.activeLength().then(console.log)