Cannot read property 'click' of undefined while using Java Script Executor in Selenium

I am getting an error:

Cannot read property 'click' of undefined

while trying to click a button using java script executor. I have tried many different approach to click the button using action classes, webdriverwait etc but none seems to work.Java Script is working in console but when i am using in my code i am unable to click the button and getting the mentioned error

The html dom looks as below:

<div>
    <a class="button button--new-resource" href="/admin/certificate_types/new">
        <img src="/assets/icon-add-user-e2a98953aa1855b15304eb16415b536ee92e579ce89f429bcdd062faa855e261.svg" alt="Icon add user"> New Certificate Type
    </a>
</div>

My selenium script is as below

JavascriptExecutor js=(JavascriptExecutor) driver;        
js.executeScript("var x= document.getElementsByClassName('button button--new-resource')[0];"+"x.click();");

from Cannot read property 'click' of undefined while using Java Script Executor in Selenium