This is because arrays have a ] internal method that knows to update length when an integer index is written to, or update the array contents when length is written to. Similarly, adding array elements automatically changes the length property. The obj.x property access syntax simply invokes the ] method on the object, and the object uses its own internal method implementation to determine what to return.Īs another example, arrays differ from normal objects, because they have a magic length property that, when modified, automatically allocates empty slots or removes elements from the array. There isn't anything special about this process in the language - it's just because ordinary objects, by default, have a ] internal method that is defined with this behavior. If x is an accessor property, the getter is invoked, and the return value of the getter is returned.

If x is a data property, the property descriptor's value attribute is returned.

The x property is searched up the prototype chain until it is found.

For example, when you read obj.x, you may expect the following to happen: However, the language doesn't provide any machinery to directly manipulate data stored in the object - rather, the object defines some internal methods specifying how it can be interacted with.

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