reading an object's attributes and properties using recursion?

Question

I wonder if it would be possible for me to employ a recursive function to read all the attributes and properties of an object including the nested properties and such. for example, if I have an object:

  var mObj = {};
  mObj.countries = [];
  mObj.country = {};
  mObj.country.states = [];
  mObj.country.state = {};
  mObj.country.state = {};

I am sure you get the picture. If it was just a simple object then I can employ "for in" loop, and perhaps nested "for in" loop, an object has numerous nested levels then using nested "for in" loops becomes somewhat chaos. I thought it would wonderful to employ recursion. Any help insight to this would highly appreciated.

Thank you.

I'd say yes you have to use recursion. Absolutely correct observation. So take a shot at it, post your code and tell us what problems you are having — ControlAltDel, May 04 '12 at 20:18
I'm slow today and I don't get the picture. Can you elaborate with a mock input Object, and describe the kind of output do you want? Like, given mObj you want those mObj.countries, states, filled in? — Heitor Chang, May 04 '12 at 20:18
In Chrome's developer tools (or Firebug, I believe) if you `console.log()` an object, it will print all of its properties recursively. I suggest you use one of those to develop, unless you want to use this information for something other than debugging. — Explosion Pills, May 04 '12 at 20:23
The duplicate line `mObj.country.state = {};` would in practice refer to two different states right? It looks like you can [use getOwnPropertyNames to define a base case](http://stackoverflow.com/questions/2673121/how-to-check-if-object-has-any-properties-in-javascript) according to CMS. getOwnPropertyNames can be recursively called on properties which themselves have properties, I would imagine, and it will return an object whose length is 0 if there are no properties in the object on which it is called. — Grayson, May 04 '12 at 20:24
@dystroy I don't see anything in the FAQ that would prohibit people from asking if a certain approach is suitable to solve a specific problem. — Anthony Grist, May 04 '12 at 20:24

score 3 · Accepted Answer · answered May 04 '12 at 20:46

Here's a quick example that does this in case you end up running into any problems.

var level = '';
var readProperties = function(val) {
    if (Object.prototype.toString.call(val) === '[object Object]') {
        for (var propertyName in val) {
            if (val.hasOwnProperty(propertyName)) {
                console.log(level + propertyName + ':');
                level += '  ';
                readProperties(val[propertyName]);
            }
        }
    }
    else {
        console.log(level + val);
        level = level.substring(0, level.length - 2);
    }
}

thank you so much. This really helps. Now I know how to tackle this. Fantastic. — Combustion007, May 08 '12 at 01:09

score 0 · Answer 2 · answered Nov 03 '15 at 08:06

Had same problem as OP, but couldn't get the accepted solution working properly. Here's what I ended up doing:

function foreachAttribute(object, handleAttributeName, handleAttributeValue) {

    var attributeNames = [];
    function recursion(object) {

        for ( var attribute in object) {

            if (typeof object[attribute] == 'object') {

                attributeNames.push(attribute);
                recursion(object[attribute]);
                attributeNames = attributeNames.slice(0,
                        attributeNames.length - 1);

            } else {

                handleAttributeName(attributeNames.join(".") + "."
                        + attribute);
                handleAttributeValue(object[attribute]);

            }

        }

    }

    recursion(object);

}

var attributeName = "";
var handleAttributeName = function(name) {
    attributeName = name;
};

var handleAttributeValue = function(value) {
    console.log(attributeName + "=" + value);
};

var data = {
    var1 : {
        asdf : 123
    },
    var2 : 321
};

foreachAttribute(data, handleAttributeName, handleAttributeValue);

reading an object's attributes and properties using recursion?

2 Answers2

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