Homologo of IndexOf in Jquery? o How to execute JavaScript attribute in Jquery?

I want to verify an Input of type Email, and get a validation once placed the .COM since it is the only thing that lacks the validation of the browser.

I was dealing with JQuery but I can not find information to help me, I need something that works equal to IndexOf of JavaScript but in Jquery, or failing that, how can I use an attribute or JavaScript function in Jquery? / p>

I remember that [0] was used to specify a JavaScript in JQuery but I do not remember its correct use.

Using something like this to validate the .com :

else if (this.value.indexOf(".com") <= 0) {
        alert("El email debe contener .com")};