Javascript Click on Element by Class

I'd suggest:

document.querySelector('.rateRecipe.btns-one-small').click();

The above code assumes that the given element has both of those classes; otherwise, if the space is meant to imply an ancestor-descendant relationship:

document.querySelector('.rateRecipe .btns-one-small').click();

The method getElementsByClassName() takes a single class-name (rather than document.querySelector()/document.querySelectorAll(), which take a CSS selector), and you passed two (presumably class-names) to the method.

References:

• document.getElementsByClassName().
• document.querySelector().

If you want to click on all elements selected by some class, you can use this example (used on last.fm on the Loved tracks page to Unlove all).

var divs = document.querySelectorAll('.love-button.love-button--loved'); 

for (i = 0; i < divs.length; ++i) {
  divs[i].click();
};

With ES6 and Babel (cannot be run in the browser console directly)

[...document.querySelectorAll('.love-button.love-button--loved')]
   .forEach(div => { div.click(); })