Writing a print_r output line break function similar to php in js

<script type="text/javascript">
<!--
var my={
str:'',
deep:0,
block:' ',
get_pre:function(n)
{
pre='';
for(i=0;i<n;i++)
{
pre+=;
}
return pre;
},
show_obj:function(obj)
{
for(k in obj)
{
if(typeof(obj[k])!='object' && typeof(obj[k])!='array')
{
pre=this.get_pre();
+=pre+k+'=>'+obj[k]+'\n';
}
else if(typeof(obj[k])=='object' && typeof(obj[k].length)=='undefined')//If it is an object
{
pre=this.get_pre();
+=pre+k+'=>OBJECT{\n';
++;//Start recursion, depth +1
this.show_obj(obj[k]);
pre = this.get_pre();
--;//Recursively ends a depth-1
+=pre+'}\n';
}
else if(typeof(obj[k])=='object' && typeof(obj[k].length)!='undefined')//If it is an array
{
pre=this.get_pre();
+=pre+k+'=>ARRAY[\n';
++;//Same object
this.show_obj(obj[k]);
pre = this.get_pre();
--;//Same object
+=pre+']\n';
}
}
return ;
},
alert_obj:function(obj)
{
alert(this.show_obj(obj))
}
}
my.alert_obj({a:{b:{c:{d:'hello world'}}}});
//-->
</script>