Pfthb

I have four <button> tags, I need that when I click on the button tag, jQuery add the class Active.

This is the code I have:

$(document).ready(function () 
 var btnActive;
 $(".cont-btn button:nth-of-type(1)").click(function () 
 btnActive = 1;
 );
 $(".cont-btn button:nth-of-type(" + btnActive + ")").click(function () 
 for (i = 0; i <= 4; i++) 
 if (i === btnActive) 
 $(".cont-btn button:nth-of-type(" + btnActive + ")").addClass("active");
 else 
 $(".cont-btn button:nth-of-type(" + i + ")").removeClass("active");
 
 
 );
);

Sorry for my English

PD. I get this error in the console at HTMLDocument.<anonymous> (proyectos.html:97)

There is a much simpler way to handle this. When you click the button remove the buttons of interest then add it to the element you clicked:

$(".cont-btn").click(function () 
 $(".cont-btn").removeClass("active");
 $(this).addClass("active");
);

Example

You are making it more complicated than it needs to be.

The following should do what you need assuming that <button> is inside class="cont-btn"

var $buttons = $(".cont-btn button").click(function () 
 $buttons.removeClass('active');
 $(this).addClass('active'); 
);

$(".cont-btn button:nth-of-type(" + btnActive + ")") this code is executed only once.

Your code may be like this

$('.cont-btn button:eq(0)').addClass('active');
$('.cont-btn button').click(function() 
 $('.cont-btn button').removeClass('active'); 
 $(this).addClass('active');
) 

P.s. I guess that you misunderstood how event handlers work. I would recommend you to read more on this topic. Execution flow in JS isn't easy to grasp.