This will produce different results in TSTL vs TS:
const a: string[] = [];
[a[0], a[0]] = ["A", "B"];
console.log(a[0]); // "A" in Lua, "B" in JS
Playground
This is because of a peculiar behavior of Lua where, even though expressions are evaluated in the same order as JS, the actual assignments happen in reverse order. This is demonstrated with this:
const a: string[] = setmetatable([], {__newindex(k, v) { console.log(v); }});
function first() { console.log("first"); return 0; }
function second() { console.log("second"); return 1; }
function third() { console.log("third"); return "A"; }
function fourth() { console.log("fourth"); return "B"; }
[a[first()], a[second()]] = [third(), fourth()]; // first, second, third, fourth, B, APlayground
This will produce different results in TSTL vs TS:
Playground
This is because of a peculiar behavior of Lua where, even though expressions are evaluated in the same order as JS, the actual assignments happen in reverse order. This is demonstrated with this:
Playground