Checkbox click in protractor angular

I am trying to execute the below statements in angular:

const checkbox = browser.driver.findElement(by.css('.1testApp-experience-checkbox')); checkbox.click();

HTML:

[class]="i+appName+'-experience-checkbox'"

(where appName is testApp and i is 0)

I am getting the below error: - Failed: invalid selector: An invalid or illegal selector was specified (Session info: chrome=68.0.3440.106) (Driver info: chromedriver=2.41.578737 (49da6702b16031c40d63e5618de03a32ff6c197e),platform=Windows NT 6.3.9600 x86_64)

How can I resolve this?