ES2022 Key Features Overview: Top-level await, Array.at(), Class Private Fields, and More

This document introduces the major changes included in ES2022 and features at the TC39 Stage 4 level. ES2022 features include 'Top-level await', which ensures the completion of asynchronous processing in modules; 'Array.prototype.at()', which enables access to array elements using negative indices; 'Object.hasOwn()', which resolves issues with the existing hasOwnProperty; 'Error cause', which preserves the cause of an error; 'Regexp Match Indices', which provides indices for regex matches and capture groups; and 'Class Fields', which includes class fields and private fields/methods/accessors declarations. Additionally, it covers the 'findLast' and 'findLastIndex' methods, which find the last element satisfying a condition from the end of an array. These are TC39 Stage 4 proposals not yet included in the official ES2022 specification but with a high likelihood of being added in 2023.