how to get object value using eval() on a string

Question

I'm playing with wikipedia json, so… I have this object:

Object {query: Object}
query: Object
    pages: Object
        869994: Object
            ns: 0
            pageid: 869994
            revisions: Array[1]
            title // <- I need you baby

retrieved with an id (in this case, 869994). Now I want to retrieve the title, so i should use

    $.getJSON(myIdUrl, function(data) {

    var obj = 'data.query.pages.' + id + '.title';

    console.log(obj); // it prints data.query.pages.869994.title should be right..

    var title = eval(obj); // now I want to assign obj title value to my variable

    // something else…      
});

I get an error, "SyntaxError: Unexpected number '.869994' "…

I think I misunderstood the eval() function, or just making the wrong path to retrieve obj data…

suggestions? thank you!

Lucas Green · Accepted Answer · 2012-09-29 19:07:28Z

2

Change this:

var obj = 'data.query.pages.' + id + '.title';

to this:

var obj = 'data.query.pages["' + id + '"].title';

The reason is that the parser is confused; when you dereference an object it's expecting an identifier, not a literal number.

var x = {};
x.5 = "test"; // <- notice this seems very unnatural

answered Sep 29, 2012 at 19:07

Lucas Green

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