[
 {
   "username": "kishan",
   "password": "patel"
 }
]

describe ('Login Page Data Driven' , function() {
  browser.ignoreSynchronization = true;


beforeEach(function(){
 browser.get('your url');
 browser.driver.manage().window().maximize();
 });

it('To verify Login, using Data Driven Technique from Json file', function()

{
 var testData = require('D:/json path'); //this is the path where your json is stored
   var user= element(by.id("username"));
   var password = element(by.id("password"));
   user.sendKeys(testData[1].username);
   password.sendKeys(testData[1].password);
});