var string = "background-image";


function camelization(str){
     str = str.toLowerCase();
     var strLen = str.length;
     var dashPosition = str.indexOf("-");
     var words = [];
     words[0] = str.substring(0, dashPosition);
     words[1] = str.substring(dashPosition + 1, strLen);
     var outp = words[0] + words[1].charAt(0).toUpperCase() + words[1].substring(1, words[1].length);

     console.log(outp);
}

camelization(string);