Accessing a JavaScript array using a value passed into a function

I have a JavaScript array declared in my JavaScript page like so:

var example = [[20,870,5,1,1,16],[28,1250,8,1,1,23]];

This works fine when accessed elsewhere.

I have a checkbox in my HTML page like so:

<input type="checkbox" id="example" onChange="update('example')">Example

I want the function to look something like below. The variable being passed is also the name of my JS array. I will have 20-30 check boxes and I would ideally like to avoid a load of if/else statements.

function update(a) {

alert(a[0][1]);

}

Is there anyway to use the variable passed into my function to access the namesake JS array?

Thanks