JSFiddle - React, Tailwind, and code Playground

JavaScript

(function (){
   var ii, val = 0; 
    
    for(ii = 0; ii < 1000; ii++){
        if(ii % 3 === 0 || ii % 5 === 0){
            val += ii
        }
           
    }
    
    alert (val);
}
)();