Javascript code to get a string sliced till last occurance of a charcter

Javascript code to get a string sliced till last occurrence of a character function
 //javascript
getStringTillLastCharcter(str,chr)
{
    var flag=0;
    var lastpos;
    //alert(str.length);
    for(i=0;i < str.length; i++ )  {
        if(str.charAt(i)==chr)
            {
                lastpos=i+1;
            }
    }
    //alert(lastpos);
    return str.slice(0,lastpos);
}

Here is a code to get the string till the last occurance of a charcter.....