This code will customize range slider's value and process

range_slider_value_customize.js

let slider = document.getElementById('ff_148_rangeslider');

let text = document.querySelector('.ff_range_value');
let text2 = document.querySelector('.ff_range_value_2');


slider.onchange=function(){
    let value = document.getElementById('ff_148_rangeslider').value;

    value *= 15;
   
    text2.innerHTML = '$ '+value;
    text2.style.display = 'block';

}