Question

If I have a string of "myArray[0].myPrice", how do I turn this in to a reference to myPrice?

This is the code context:

binding.value = convert(binding.data[binding.field], 
                        binding.converter, binding.data, elem); 

binding.field is what contains “myArray[0].myPrice”.

binding.data has a reference to the hierarchical object which has an Array property of myArray, and the first element is an object with a property of myPrice.

EDIT: based on the answers, this worked:

binding.value = convert(eval('(binding.data.' + binding.field + ')'), 
              binding.converter, binding.data, elem);

Is it good to use eval like this? I thought eval was going away in newer JavaScript?

Answer 1

You can use eval, but here is a better solution:

// The following code results in the same as that scary eval(...)

var data = binding.data,
    chain = binding.field.split(/[\.\[\]]+/);

for (var i = 0; data[chain[i]]; i++) {
    data = data[chain[i]];      
}

// Embrace JavaScript Awesomeness!

A breakdown of what I’m doing here:

In JS any property can be called as object[propertyName].

That includes arrays, i.e. a[3] is the same as a['3'].

Therefore, we split the string using one of the characters: ., [, ]. The + is there because without it if you have a[3].b[3] the ]. will give you an empty
string.

We might get an empty string in the end, but that’s not a problem since "" is like false in JS.

You could go further and filter out all the invalid variable names, which in javascript is a name that does not conform to [a-zA-Z_$][0-9a-zA-Z_$]*. But I am not quite sure as to why one would do that…