I want firefox sources ~/.firefoxrc automatically when I open a webpage.
~/.firefoxrc contains several javascript functions:

Array.prototype.sum = function(){
    for(var i=0,sum=0;i<this.length;sum+=this[i++]);
    return sum;
}
Array.prototype.max = function(){
    return Math.max.apply({},this)
}
Array.prototype.min = function(){
    return Math.min.apply({},this)
}

So I can use these functions in firebug console.