javascript convert dotnotation string into objects

Question

I have a string like this "namespace.fun1.fun2.fun3" passed from the client. It's telling the server which function to use.

How do I safely run the function?

right now i'm doing:

var runthis = string.split('.')
namespace[runthis[1]][runthis[2]][runthis[3]]

How do I handle arbitrary depth of nesting safely?

jAndy · Accepted Answer · 2011-07-15 10:08:28Z

5

A little function I wrote. I use it in most of my applications:

Object.lookup = (function _lookup() {
    var cache = { };

    return function _lookupClosure( lookup, failGracefully ) {
        var check   = null,
            chain   = [ ],
            lastkey = '';

        if( typeof lookup === 'string' ) {
            if( cache[ lookup ] ) {
                chain = cache[ lookup ].chain;
                check = cache[ lookup ].check;
            }
            else {
                lookup.split( /\./ ).forEach(function _forEach( key, index, arr ) {
                    if( check ) {
                        if( typeof check === 'object' ) {
                            if( key in check ) {
                                chain.push( check = check[ key ] );
                                lastkey = key;
                            }
                            else {
                                if( !failGracefully ) {
                                    throw new TypeError( 'cannot resolve "' + key + '" in ' + lastkey );    
                                }
                            }
                        }
                        else {
                            if( !failGracefully ) {
                                throw new TypeError( '"' + check + '" ' + ' does not seem to be an object' );   
                            }
                        }
                    }
                    else {
                        lastkey = key;
                        chain.push( check = window[ key ] );
                    }
                });

                if( check ) {
                    cache[ lookup ] = {
                        chain: chain,
                        check: check
                    };
                }
            }
        }

        return {
            execute: function _execute() {
                return typeof check === 'function' ? check.apply( chain[chain.length - 2], arguments ) : null;
            },
            get: function _get() {
                return check;
            }
        };
    }
}());

usage:

Object.lookup( 'namespace.fun1.fun2.fun3' ).execute();

The first parameter is the object/method/property to resolve. The second (optional) parameter indicates whether or not the lookup() method shall fail silently or throw an exception if some property or object could not get resolved. default is 'throw'. To avoid that call

Object.lookup( 'namespace.fun1.fun2.fun3', true ).execute( 'with', 'paras' );

If .fun3 is a function, you can pass in any parameters into .execute() instead. if you just want to receive the property value, you can also call .get() instead of .execute()

var val = Object.lookup( 'namespace.fun1.fun2.fun3' ).get();

edited Jul 15, 2011 at 10:08

answered Jul 15, 2011 at 9:02

jAndy

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5 Comments

Alex Wayne Over a year ago

That's likely far more complex that this needs here.

jAndy Over a year ago

@Squeegy: I don't see the 'complex' part.Probably the local caching ? which is a pretty good idea if you're using such a function quite a lot.

jAndy Over a year ago

@Harry: well I've updated the method. Should work better now.

jAndy Over a year ago

@Harry: Oh true, you need just to replace it by global

Harry Over a year ago

Why check === 'object'? Should be fine if it's also a function right.

rubergly · Accepted Answer · 2011-07-15 09:15:23Z

2

(I may be misinterpreting the question, but this is what came to mind)

var s = "space.f.g.h.i.j.k.l.m",
  a = s.split( "." ),
  fn = eval( a[0] );

for ( var i = 1; i < a.length; i++ ) {
  fn = fn[ a[i] ];
}

fn();

Note: this won't guard against the namespace being specified incorrectly or maliciously.

edited Jul 15, 2011 at 9:15

answered Jul 15, 2011 at 9:07

rubergly

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2 Comments

davin Over a year ago

That's unsafe. You're allowing a client to run you into a TypeError without even making it hard...

jAndy Over a year ago

furthermore, I would avoid eval() at all costs in a server-environment. Especially if the data comes from somewhere else (like in this case). Asking for terrible trouble.

chjj · Accepted Answer · 2011-07-15 09:13:46Z

1

This should do:

var get = function(obj, key) {
  var s = key.split('.')
    , i = 1
    , l = s.length;

  for (; i < l; i++) {
    obj = obj[s[i]];
    if (!obj) return;
  }

  return obj;
};

get({hello:{world:{}}}, 'ns.hello.world');

edit: changed code a bit

answered Jul 15, 2011 at 9:13

chjj

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Comments

Alex Wayne · Accepted Answer · 2011-07-15 09:26:49Z

1

Here's a simple for loop that should do find each object specified strating from the global scope, and then run the function it finds.

window.namespace = { fun1: { fun2: { fun3: function() { alert('hi!') }}}};

runFunc = function(address) {
    var addressArray = address.split('.'),
        current = window,
        i = 0;

    for (i = 0; i < addressArray.length; i++) {
        current = current[addressArray[i]];
    }

    current();
};

runFunc('namespace.fun1.fun2.fun3');

http://jsfiddle.net/jfWra/1/

And here's some eror protection that will throw something meaningful if the value referenced doesnt exist or is not a function: http://jsfiddle.net/jfWra/2/

edited Jul 15, 2011 at 9:26

answered Jul 15, 2011 at 9:17

Alex Wayne

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1 Comment

jAndy Over a year ago

this will fail if any level is missing.

Liudmil Mitev · Accepted Answer · 2011-07-15 10:02:56Z

0

Here's another simple solution using a recursive function:

function run(str, context) {
  var path = str.split(".")
  if path.length == 1 {
     context[path[0]].call()
     return;
  }

  if(typeof context == 'undefined') {
     context = window[path[0]]
  } else {
     context = context[path[0]]
  }
  run(path.splice(1).join('.'), context)
}

answered Jul 15, 2011 at 10:02

Liudmil Mitev

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Comments

djromero · Accepted Answer · 2014-03-03 14:49:28Z

0

Two years later there is this module: https://github.com/daaku/nodejs-dotaccess.

var get = require("dotaccess").get;
var o = {a:{b:{c:'deep'}}};
console.log(get(o, 'a.b.c'));

answered Mar 3, 2014 at 14:49

djromero

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