Why do I get a different type dependant on when I evaluate a JavaScript variable in Salesforce Lightning

Question

I would like to understand why the typeof a JavaScript variable is different depending on where I evaluate it, even though I have't changed it.

I have a object like this:

var model = {}
model.user = {}
model.caller = {}
model.caller.name = 'Batman';
model.other = {}
// etc

I pass it into a child Lightning component like this:

$A.createComponent(screen, {
        "aura:id" : "activeScreen",
        "model" : model
    }, function (contentComponent, status, error) {
        if (status === "SUCCESS") {
            target.set('v.body', [contentComponent]);
        } else if (status === "INCOMPLETE") {
            console.log("No response from server or client is offline.")
        } else if (status === "ERROR") {
            throw new Error(error);
        }
    });

It's stored in this attribute in the child component:

<aura:attribute name="model" type="Object" />

And in the child component get the model using this helper method:

model : function(cmp) {
    return cmp.get("v.model");
},

If I call this method and check the typeof the value return:

var model = helper.model(cmp);
console.log(typeof model);

I get an console out put of:

string

Whereas, if I evaluate the value within the helper method:

model : function(cmp) {

    var model = cmp.get("v.model");

    switch (typeof model){
        case 'string':
            console.log('string');  
            return JSON.parse(cmp.get("v.model"));

        case 'object':
            console.log('object');  
            return cmp.get("v.model");
    }

    return null;
},

The console out put is:

object

Why do I get a different type dependant on when I evaluate it?

Answer 1

This is not an answer to:

Why do I get a different type dependant on when I evaluate it?

But if you are battling this issue, the below might help.

---

By setting the attribute type to string I consistently get an object

<aura:attribute name="model" type="String" />

Seem backwards... but it works... at the moment (June 2018)