In parallel? Currently, native JS does not have SIMD instructions or similar to iterate over data in parallel. What you can do, however:
const arr = [
{ foo: 1 },
{ foo: 2 },
{ foo: 3 },
];
// blocking (sync)
arr.forEach(
obj => console.log(obj.foo)
);
// non-blocking (async)
arr.forEach(
obj => setTimeout(() => console.log(obj.foo), 0)
);
Well, if you want to iterate over an array in parallel (and possibly do an operation on each item), and want to use WebDev and not limit yourself to JS only, you can do so by using WASM, which allows you to either use native SIMD (C, C++) or multithreading (C, C++, Rust).