JSFiddle - React, Tailwind, and code Playground

HTML

<input type="radio" name="fpago" id="fpago1" value="1" />one
<input type="radio" name="fpago" id="fpago2" value="2" />two
<br>
<span id="myspan" >bla bla</span>

<input type="hidden" id="id_grupo" value="1" />

JavaScript

$(document).ready(function() {
	$("#myspan").hide();//hide it by default
		
	$("#fpago1, #fpago2").bind('change click',function(){
		togglePlazo();
	});
	
	//in this case, id_grupo is "1" so shuld check the radio AND show the span...
	grupo = $("#id_grupo").val();
	if(grupo != '0'){
		$("#fpago2").attr('checked', true); //<-- it does check it but it doesn't trigger the function (i.e. the span doesn't show)
        //of course i could just add a ".click()" to my selector to ensure to trigger, but it should not be necesary, since I already bound it .
	}
	
});

function togglePlazo(){
       
	plazo = $("[name='fpago']:checked").val();
	//alert(plazo);
    
	if(plazo == "2"){
		$("#myspan").show();		
	}else{
		$("#myspan").hide();		
	}	
}