There is an error in example ?

[a1mersnow]

let o = { f(x, y) { return x + y + this.z; }, z: 0 };

const g = o.f(?, 3);
g(1); // 4

// replace the value of `o`
o = { f(x, y) { return x + y + this.z; }, z: 2 };
g(1); // 6

// replace the value of `o.f`
o.f = (x, y) => x * y;
g(1); // 5

the last one should be 3 ?

[rbuckton]

This example was removed in a recent update. Current examples should be clearer.