A+B

function addition(a,b){
    var r = "", z = "", i, s = 0;
    if( a.length > b.length ){
        i=0; while( i<a.length-b.length ){ z+="0"; i++;} b=z+b;
    }else{
        i=0; while( i<b.length-a.length ){ z+="0"; i++;} a=z+a;
    }
    for(i=0;i<a.length;i++){
        var ch = parseInt(a[a.length-1-i])+
                parseInt(b[a.length-1-i])+s;
        var m = ch%10;
        r = m + r;
        s = (ch-m)/10;
    }
    return r;
}