{"id":6511,"date":"2021-12-24T08:43:49","date_gmt":"2021-12-23T23:43:49","guid":{"rendered":"https:\/\/www.sria.co.jp\/blog\/?p=6511"},"modified":"2021-12-24T08:43:49","modified_gmt":"2021-12-23T23:43:49","slug":"6511","status":"publish","type":"post","link":"https:\/\/www.sria.co.jp\/blog\/2021\/12\/6511\/","title":{"rendered":"\u3010ES2022\u3011\uff08JavaScript\uff092022\u5e74\u516c\u958b\u4e88\u5b9a\u6a5f\u80fd"},"content":{"rendered":"

\u3069\u3082\u3001\u30ab\u30ed\u30fc\u30b8\u3067\u3059\u3002<\/p>\n

2015\u5e74\u4ee5\u964d\u6bce\u5e74\u6539\u5b9a\u3055\u308c\u3066\u3044\u308bJS\u306eECMA\u898f\u683c\u306b\u3064\u3044\u30662022\u5e74\u516c\u958b\u4e88\u5b9a\u306e\u6a5f\u80fd\u306b\u3064\u3044\u3066\u3067\u3059\u3002<\/p>\n

\u300cfinished-proposals.md<\/a>\u300d\u30d5\u30a1\u30a4\u30eb\u3067\u3001Expected Publication Year\u304c2022\u5e74\u306b\u306a\u3063\u3066\u3044\u308b\u6a5f\u80fd\u3092\u53d6\u308a\u4e0a\u3052\u307e\u3057\u305f\u3002<\/p>\n

ES2022\u306b\u4e88\u5b9a\u3055\u308c\u3066\u3044\u308b\u6a5f\u80fd<\/h2>\n

1. Class Fields
\n1-1. Private instance methods and accessors<\/a><\/h3>\n

\u4ee5\u4e0b\u306e\u69d8\u306a\u611f\u3058\u3067\u3001\u30a2\u30af\u30bb\u30b5\uff08getter\u3084setter\uff09\u3084\u30e1\u30bd\u30c3\u30c9\u306b\u300c#\u300d\u3092\u3064\u3051\u308b\u3068\u30d7\u30e9\u30a4\u30d9\u30fc\u30c8\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n

\n
class Counter extends HTMLElement {\n#xValue = 0;\n\nget #x() { return #xValue; }\nset #x(value) {\nthis.#xValue = value;\nwindow.requestAnimationFrame(this.#render.bind(this));\n}\n\n#clicked() {\nthis.#x++;\n}\n}<\/code><\/pre>\n<\/div>\n
1-2. Class Public Instance Fields & Private Instance Fields<\/a><\/h3>\n
\u30d7\u30ed\u30d1\u30c6\u30a3\u306b\u53ef\u8996\u6027\uff08\u30d1\u30d6\u30ea\u30c3\u30af\u3001\u30d7\u30e9\u30a4\u30d9\u30fc\u30c8\uff09\u3092\u8ffd\u52a0\u3067\u304d\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002
\n\u30d7\u30ed\u30d1\u30c6\u30a3\u306b\u300c#\u300d\u3092\u3064\u3051\u308b\u3068\u30d7\u30e9\u30a4\u30d9\u30fc\u30c8\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n
1-3. Static class fields and private static methods<\/a><\/h3>\n
\u300cstatic\u300d\u304c\u4f7f\u3048\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002\u9759\u7684\u306a\u30d7\u30ed\u30d1\u30c6\u30a3\u3084\u30e1\u30bd\u30c3\u30c9\u304c\u4f7f\u3048\u307e\u3059\u3002<\/p>\n
\n
class CustomDate {\n\/\/ ...\nstatic epoch = new CustomDate(0);\n}<\/code><\/pre>\n<\/div>\n
2. RegExp Match Indices<\/a><\/h3>\n
\u30ec\u30ae\u30e5\u30e9\u30fc\u30a8\u30af\u30b9\u30d7\u30ec\u30c3\u30b7\u30e7\u30f3\u306b\u3088\u308b\u6b63\u898f\u8868\u73fe\u3067\u3001\u30de\u30c3\u30c1\u3057\u305f\u4f4d\u7f6e\u60c5\u5831\u304c\u8ffd\u52a0\u3055\u308c\u308b\u3002
\n\u305f\u3060\u3057\u3001\/d\u306e\u30aa\u30d7\u30b7\u30e7\u30f3\u304c\u5fc5\u8981\u3068\u306e\u3053\u3068\u3002<\/p>\n
\n
const re1 = \/a+(?<Z>z)?\/d;<\/code><\/pre>\n<\/div>\n
3. Top-level await<\/a><\/h3>\n
async \/ await\u306e\u5b9a\u7fa9\u304c\u30e1\u30bd\u30c3\u30c9\u306e\u4ed6\u306b\u3001\u30e2\u30b8\u30e5\u30fc\u30eb\u3067\u3082\u4f7f\u7528\u53ef\u80fd\u3068\u306e\u3053\u3068\u3002
\n\u30e2\u30b8\u30e5\u30fc\u30eb\u306e\u6982\u5ff5\u304c\u4ed5\u69d8\u4e0a\u3069\u3046\u306a\u3063\u3066\u308b\u306e\u304b\u6c17\u306b\u306a\u308b\u3002\u305d\u3057\u3066deno\u307f\u305f\u3044\u3002<\/p>\n
\n
const strings = await import(`\/i18n\/${navigator.language}`);<\/code><\/pre>\n<\/div>\n
4. Ergonomic brand checks for Private Fields<\/a><\/h3>\n
\u300c\u30d7\u30e9\u30a4\u30d9\u30fc\u30c8\u30d5\u30a3\u30fc\u30eb\u30c9\u306e\u4eba\u9593\u5de5\u5b66\u7684\u30d6\u30e9\u30f3\u30c9\u30c1\u30a7\u30c3\u30af\u300d\u3046\u30fc\u3093\u3002\u5b57\u9762\u3060\u3051\u3060\u3068\u30e8\u30af\u308f\u304b\u3089\u306a\u3044\u3002\u3002<\/p>\n
Try\/Catch\/Exception\u3092\u4f7f\u7528\u3057\u306a\u304f\u3068\u3082\u3001\u300cin\u300d\u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u3067\u30d7\u30e9\u30a4\u30d9\u30fc\u30c8\u30d5\u30a3\u30fc\u30eb\u30c9\u306e\u6709\u7121\u304c\u5206\u304b\u308a\u3088\u3046\u306b\u306a\u308b\u3002\u3068\u306e\u3053\u3068<\/p>\n
\n
class C {\n#brand;\n\n#method() {}\n\nget #getter() {}\n\nstatic isC(obj) {\nreturn #brand in obj && #method in obj && #getter in obj;\n}\n}<\/code><\/pre>\n<\/div>\n
5. .at()<\/a><\/h3>\n
Array\u3001String\u3001TypedArray\u306b\u3001\u6307\u5b9a\u4f4d\u7f6e\u306e\u5024\u304c\u53d6\u5f97\u51fa\u6765\u308b\u30e1\u30bd\u30c3\u30c9\u3067\u3059\u3002
\n\u305f\u3060\u3001Polyfill\u898b\u305f\u611f\u3058\u3001\u8ca0\u306e\u5024\u306e\u6271\u3044\u304c\u5fae\u5999\u306a\u611f\u3058\u304c\u3057\u307e\u3059\u3002\u3002<\/p>\n
\n
function at(n) {\n\/\/ ToInteger() abstract op\nn = Math.trunc(n) || 0;\n\/\/ Allow negative indexing from the end\nif (n < 0) n += this.length;\n\/\/ OOB access is guaranteed to return undefined\nif (n < 0 || n >= this.length) return undefined;\n\/\/ Otherwise, this is just normal property access\nreturn this[n];\n}<\/code><\/pre>\n<\/div>\n
6. Accessible Object.prototype.hasOwnProperty<\/a><\/h3>\n
\u3046\u30fc\u3093\u3002\u3088\u304f\u308f\u304b\u3089\u306a\u304b\u3063\u305f\u3002\u5206\u304b\u308a\u6b21\u7b2c\u3001\u63b2\u8f09\u3057\u307e\u3059\u3002<\/p>\n
7. Class Static Block<\/a><\/h3>\n
\u9759\u7684\u30d6\u30ed\u30c3\u30af\u306a\u308b\u3082\u306e\u304c\u4f7f\u7528\u53ef\u80fd\u306b\u306a\u308b\u3068\u306e\u3053\u3068\u3002
\n\u4f55\u304b\u3057\u3089\u306e\u8a08\u7b97\u5024\u306a\u3069\u3001\u521d\u671f\u5024\u3068\u3057\u3066\u8a55\u4fa1\u7d50\u679c\u3092\u9759\u7684\u306b\u4fdd\u6301\u3057\u305f\u3044\u5834\u5408\u3001\u9759\u7684\u30d6\u30ed\u30c3\u30af\u3092\u5b9a\u7fa9\u3059\u308b\u3053\u3068\u3067\u4f7f\u7528\u53ef\u80fd\u306b\u306a\u308a\u307e\u3059\u3002
\n\u30af\u30e9\u30b9\u304c\u8aad\u307f\u8fbc\u307e\u308c\u305f\u30bf\u30a4\u30df\u30f3\u30b0\u3067\u8a55\u4fa1\u3055\u308c\u308b\u3002\u3068\u306e\u3053\u3068<\/p>\n
\n
\/\/ \"friend\" access (same module)\nlet A, B;\n{\nlet friendA;\n\nA = class A {\n#x;\n\nstatic {\nfriendA = {\ngetX(obj) { return obj.#x },\nsetX(obj, value) { obj.#x = value }\n};\n}\n};\n\nB = class B {\nconstructor(a) {\nconst x = friendA.getX(a); \/\/ ok\nfriendA.setX(a, x); \/\/ ok\n}\n};\n}<\/code><\/pre>\n<\/div>\n
8. Error Cause<\/a><\/h3>\n
\u30a8\u30e9\u30fc\u304c\u9023\u9396\u3057\u305f\u3068\u304d\u306b\u3001.cause\u3067\u9061\u308c\u308b\u69d8\u306b\u306a\u308b\u3068\u306e\u3053\u3068\u3002<\/p>\n
\n
async<\/span> function<\/span> doJob<\/span>(<\/span>)<\/span> {<\/span>\n  const<\/span> rawResource<\/span> =<\/span> await<\/span> fetch<\/span>(<\/span>'\/\/domain\/resource-a'<\/span>)<\/span>\n    .<\/span>catch<\/span>(<\/span>err<\/span> =><\/span> {<\/span>\n      throw<\/span> new<\/span> Error<\/span>(<\/span>'Download raw resource failed'<\/span>,<\/span> {<\/span> cause<\/span>: err<\/span> }<\/span>)<\/span>;<\/span>\n    }<\/span>)<\/span>;<\/span>\n  const<\/span> jobResult<\/span> =<\/span> doComputationalHeavyJob<\/span>(<\/span>rawResource<\/span>)<\/span>;<\/span>\n  await<\/span> fetch<\/span>(<\/span>'\/\/domain\/upload'<\/span>,<\/span> {<\/span> method<\/span>: 'POST'<\/span>,<\/span> body<\/span>: jobResult<\/span> }<\/span>)<\/span>\n    .<\/span>catch<\/span>(<\/span>err<\/span> =><\/span> {<\/span>\n      throw<\/span> new<\/span> Error<\/span>(<\/span>'Upload job result failed'<\/span>,<\/span> {<\/span> cause<\/span>: err<\/span> }<\/span>)<\/span>;<\/span>\n    }<\/span>)<\/span>;<\/span>\n}<\/span>\n\ntry<\/span> {<\/span>\n  await<\/span> doJob<\/span>(<\/span>)<\/span>;<\/span>\n}<\/span> catch<\/span> (<\/span>e<\/span>)<\/span> {<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>e<\/span>)<\/span>;<\/span>\n  console<\/span>.<\/span>log<\/span>(<\/span>'Caused by'<\/span>,<\/span> e<\/span>.<\/span>cause<\/span>)<\/span>;<\/span>\n}<\/span>\n\/\/ Error: Upload job result failed<\/span>\n\/\/ Caused by TypeError: Failed to fetch<\/span><\/pre>\n<\/div>\n
\u307e\u3068\u3081<\/h2>\n
\u3042\u308c\uff1f\u4eca\u307e\u3067\u7121\u304b\u3063\u305f\u306e\uff1f\u7684\u306a\u6a5f\u80fd\u3082\u591a\u3005\u3042\u308a\u307e\u3059\u304c\u3001\u3069\u308c\u3082\u6709\u7528\u306a\u611f\u3058\u3067\u3059\u3002<\/p>\n
\u500b\u4eba\u7684\u306b\u306f\u8a00\u8a9e\u306b\u306a\u308a\u5207\u308c\u3066\u3044\u306a\u3044\u8a00\u8a9e\uff08\u30cb\u30e5\u30a2\u30f3\u30b9\u304c\u96e3\u3057\u3044\u3067\u3059\u304c\uff09\u81ea\u7531\u5ea6\u304c\u3042\u3063\u3066\u4e2d\u9593\u7684\u306a\u3068\u3053\u308d\u304c\u597d\u304d\u3067\u3057\u305f\u304c<\/p>\n
\u53ef\u8996\u6027\u304c\u8ffd\u52a0\u306b\u306a\u3063\u305f\u308a\u3001\u30b9\u30bf\u30c6\u30a3\u30c3\u30af\u304c\u8ffd\u52a0\u306b\u306a\u3063\u305f\u308a\u3068\u3001\u3059\u3063\u304b\u308a\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u6307\u5411\u306a\u8a00\u8a9e\u306b\u306a\u3063\u305f\u611f\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n
\u6a5f\u4f1a\u304c\u3042\u308c\u3070\u4eca\u5e74\uff082021\u5e74\uff09\u8ffd\u52a0\u3068\u306a\u3063\u305f\u6a5f\u80fd\u3082\u8a18\u4e8b\u306b\u3057\u3066\u307f\u305f\u3044\u3068\u601d\u3044\u307e\u3059\u3002<\/p>\n
 <\/p>\n
\u3067\u308f<\/p>\n","protected":false},"excerpt":{"rendered":"
\u3069\u3082\u3001\u30ab\u30ed\u30fc\u30b8\u3067\u3059\u3002 2015\u5e74\u4ee5\u964d\u6bce\u5e74\u6539\u5b9a\u3055\u308c\u3066\u3044\u308bJS\u306eECMA\u898f\u683c\u306b\u3064\u3044\u30662022\u5e74\u516c\u958b\u4e88\u5b9a\u306e\u6a5f\u80fd\u306b\u3064\u3044\u3066\u3067\u3059\u3002 \u300cfinished-proposals.md\u300d\u30d5\u30a1\u30a4\u30eb\u3067\u3001Expected Publication …<\/p>\n","protected":false},"author":5,"featured_media":6512,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[14,8,23],"tags":[282,281,49],"_links":{"self":[{"href":"https:\/\/www.sria.co.jp\/blog\/wp-json\/wp\/v2\/posts\/6511"}],"collection":[{"href":"https:\/\/www.sria.co.jp\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.sria.co.jp\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.sria.co.jp\/blog\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/www.sria.co.jp\/blog\/wp-json\/wp\/v2\/comments?post=6511"}],"version-history":[{"count":5,"href":"https:\/\/www.sria.co.jp\/blog\/wp-json\/wp\/v2\/posts\/6511\/revisions"}],"predecessor-version":[{"id":6517,"href":"https:\/\/www.sria.co.jp\/blog\/wp-json\/wp\/v2\/posts\/6511\/revisions\/6517"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.sria.co.jp\/blog\/wp-json\/wp\/v2\/media\/6512"}],"wp:attachment":[{"href":"https:\/\/www.sria.co.jp\/blog\/wp-json\/wp\/v2\/media?parent=6511"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.sria.co.jp\/blog\/wp-json\/wp\/v2\/categories?post=6511"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.sria.co.jp\/blog\/wp-json\/wp\/v2\/tags?post=6511"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}