js проверка id у section

const elements = document.querySelectorAll('section[id^=portfolios-]') 
 
for (el of elements) { 
  el.style.color = 'red' 
}

<section id="portfolios-xxx">portfolios-xxx</section> 
<section id="port-aaaa">port-aaaa</section> 
<section id="1337portfolios321">1337portfolios321</section> 
<section id="portfolios-aaaa">portfolios-aaaa</section>

$.each( $("section"), function( key, value ) { 
  if($(value).attr("id").indexOf("portfolios-") != -1) 
  { 
    alert($(value).attr("id")) 
  } 
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> 
<section id="portfolios-aaa"></section> 
<div></div> 
<div></div> 
<div></div> 
<div></div> 
<section id="portfolios-bbb"></section> 
<section id="sections-aaa"></section>

var objSections = document.getElementsByTagName('section'); 
var len = objSections.length; 
 
for (var i = 0; i < len; i++) { 
  if(objSections[i].id.indexOf("portfolios-") != -1) 
  { 
    alert(objSections[i].id) 
  } 
}

<section id="portfolios-aaa"></section> 
<div></div> 
<div></div> 
<div></div> 
<div></div> 
<section id="portfolios-bbb"></section> 
<section id="sections-aaa"></section>

let checkId = document.getElementsByTagName('section'); 
for (item of checkId){ 
    if(~item.id.indexOf("portfolios-")) 
  { 
    console.log(item.id); 
  } 
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> 
<section id="portfolios-xxx"> 
<section id="port-aaaa"> 
<section id="portfolios321"> 
<section id="portfolios-aaaa">