Javascript data structures

Question

I would like to know if it is possible to do something like this:

if (mb == null || typeof (mb) != "object") {
    var mb = new Object();
}


mb = {
    tests: {
        onAnimals: {
            test: function() {
                return "";
            }
        }
        onHumans: {
            test: function() {
                return "";
            }
        }
    }
}

Bu when I tries it, I can see Tests, but when I dot further in, I can't se onAnimals / onHumans.

javascript is still new to me, so hope you can help.

Jerod Venema · Accepted Answer · 2009-12-03 15:38:33Z

7

You're missing a comma before onHumans. I've assumed mb to be a global variable; you can use var instead if that's what you need. Also, it's easier to read if you structure it differently, like this:

window.mb = window.mb || {};
window.mb = {
  tests: {
    onAnimals: {
      test: function(){
        return "";
      }
    },
    onHumans: {
      test: function(){
        return "";
      }
    }
  }
};

answered Dec 3, 2009 at 15:38

Jerod Venema

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2 Comments

Chris Over a year ago

What good does the top line serve? You're reassigning window.mb on the second line, which negates the top line entirely, unless I'm missing something.

Jerod Venema Over a year ago

You're correct; it was just a replication of the OP code. Typically, I'd use that first line, plus Object.extend(window.mb, { ..def...}), but there's no description of what, if any, library is used.

jitter · Accepted Answer · 2009-12-03 15:41:03Z

2

You are missing a comma before onHumans

if (mb == null || typeof (mb) != "object") {
    var mb = new Object();
}

mb = {
    tests: {
        onAnimals: {
            test: function() {
                return "animal";
            }
        },
        onHumans: {
            test: function() {
                return "human";
            }
        }
    }
}

alert(mb); //[object Object]
alert(mb.tests); //[object Object]
alert(mb.tests.onAnimals); //[object Object]
alert(mb.tests.onHumans); //[object Object]
alert(mb.tests.onAnimals.test()); //animal
alert(mb.tests.onHumans.test()); //human

answered Dec 3, 2009 at 15:41

jitter

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Comments

nickf · Accepted Answer · 2009-12-03 15:39:56Z

1

You don't need to declare the variable as an object beforehand, simply using the brackets like that is all you need. You do have a syntax error, missing a commas before "onHumans", but aside from that, it looks good to me. You should be able to reach the functions via mb.tests.onAnimals.test and mb.tests.onHumans.test

answered Dec 3, 2009 at 15:39

nickf

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Comments

David Hedlund · Accepted Answer · 2010-09-23 15:36:35Z

1

Your code is mostly valid, and you don't even have to do the initial if-check. Just type var mb = { ..., and you'll start set mb to a new object, regardless of whether it was one before, or undefined, or something else...

What you're missing is a comma after the onAnimals declaration tho:

mb = {
    tests: {
        onAnimals: {
            test: function() {
                return "";
            }
        },
        onHumans: {
            test: function() {
                return "";
            }
        }
    }
}

edited Sep 23, 2010 at 15:36

answered Dec 3, 2009 at 15:39

David Hedlund

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Comments

techie.trumpet · Accepted Answer · 2010-09-23 16:10:06Z

As stated in some of the comments above testing for the existence of the variable mb is redundant when you just re-declare it to append your methods and properties.

If you are testing for the existence of the variable to add additional methods to the object you should use a method like jQuery's extend or ExtJs's apply method.

jQuery:

window.mb = $.extend(window.mb||{}, {
    tests: {
        onAnimals: {
            test: function() {
                return "";
            }
        },
        onHumans: {
            test: function() {
                return "";
        }
    }
});

Ext:

window.mb = Ext.apply(window.mb||{}, {
    tests: {
        onAnimals: {
            test: function() {
                return "";
            }
        },
        onHumans: {
            test: function() {
                return "";
        }
    }
});

This snippet of code will either append the tests object to the existing mb variable or create the mb variable then append the tests object to it.

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