JSFiddle - React, Tailwind, and code Playground

JavaScript

var str = 'assd';



var newstr = '';

for (var i = 0; i < str.length; i++) {
    
    
    if (str[i] == 'a' || str[i] == 'y') { // add whatewer letters
        
        newstr += str[i];
        
    }
}

alert(newstr);