test the existence of property in a deep object structure

Question

In javascript, lets say I want to access a property deep in an object, for example:

entry.mediaGroup[0].contents[0].url

At any point along that structure, a

Answer 1

Here's the one i have been using for a while

   var obj = { a: { b: [
                        { c: {d: 'XYZ'} }
                    ] } };

    // working

    obj.a.b[0].c.d = null;
    console.log('value:'+getProperty(obj, 'a.b[0].c.d', 'NOT-AVAILABLE')); // value:null

    obj.a.b[0].c.d = 'XYZ';
    console.log('value:'+getProperty(obj, 'a.b[0].c.d', 'NOT-AVAILABLE')); // value:XYZ
    console.log('value:'+getProperty(obj, 'a.b[0].c.d.k.sds', 'NOT-AVAILABLE')); // value:NOT-AVAILABLE

    obj.a.b[0].c = null;
    console.log('value:'+getProperty(obj, 'a.b[0].c.d', 'NOT-AVAILABLE'));  // value:NOT-AVAILABLE


    // will not work
    //console.log('v:'+getProperty(obj, 'a.b["0"].c.d'));

Here's the function

function getProperty(obj, str, defaultValue){

    var props = str.split('.').map(function(prop){
        var arrAccessRegEx = /(.*)\[(.*)\]/g;
        if (arrAccessRegEx.test(prop)){
            return prop.split(arrAccessRegEx).filter(function(ele){return ele!=''; });
        } else {
            var retArr = [];
            retArr.push(prop);
            return retArr
        };
    });

    //console.log(props);

    for(var i=0;i