Accessing array[-1]
In some programming languages, we can access array elements using negative indexes, counted from the end.
Like this:
let array = [1, 2, 3]; array[-1]; // 3, the last element array[-2]; // 2, one step from the end array[-3]; // 1, two steps from the endIn other words, array[-N] is the same as array[array.length - N].
Create a proxy to implement that behavior.
That’s how it should work:
let array = [1, 2, 3]; array = new Proxy(array, { /* your code */ }); alert( array[-1] ); // 3 alert( array[-2] ); // 2 // Other array functionality should be kept "as is"let array = [1, 2, 3]; array = new Proxy(array, { get(target, prop, receiver) { if (prop < 0) { // even if we access it like arr[1] // prop is a string, so need to convert it to number prop = +prop + target.length; } return Reflect.get(target, prop, receiver); } }); alert(array[-1]); // 3 alert(array[-2]); // 2