{"id":774,"date":"2018-12-14T12:08:42","date_gmt":"2018-12-14T04:08:42","guid":{"rendered":"https:\/\/sora.sound.moe\/?p=774"},"modified":"2018-12-14T12:08:42","modified_gmt":"2018-12-14T04:08:42","slug":"%e7%bf%bb%e8%af%91-%e5%8a%a0%e9%80%9f%e5%b1%95%e5%bc%80%e5%85%83%e7%b4%a0","status":"publish","type":"post","link":"https:\/\/sora.sound.moe\/?p=774","title":{"rendered":"[\u7ffb\u8bd1] \u52a0\u901f\u5c55\u5f00\u5143\u7d20"},"content":{"rendered":"\n<h1 id=\"speeding-up-spread-elements\">Speeding up spread elements<\/h1>\n\n\n\n<ul><li>\u539f\u6587&nbsp;<a href=\"https:\/\/v8.dev\/blog\/spread-elements\">https:\/\/v8.dev\/blog\/spread-elements<\/a><\/li><\/ul>\n\n\n\n<p>Hai Dong \u5728\u4ed6\u4e8eV8\u56e2\u961f\u7684\u4e09\u4e2a\u6708\u5b9e\u4e60\u671f\u95f4\uff0c\u81f4\u529b\u4e8e\u63d0\u5347<code>[...array]<\/code>\u3001<code>[...string]<\/code>\u3001<code>[...set]<\/code>\u3001<code>[...map.keys()]<\/code>\u4ee5\u53ca<code>[...map.values()]<\/code>\uff08\u5f53\u5c55\u5f00\u7684\u5143\u7d20\u4f4d\u4e8e\u6570\u7ec4\u5b57\u9762\u91cf\u7684\u8d77\u59cb\uff09\u3002\u4ed6\u751a\u81f3\u8ba9<code>Array.from(iterable)<\/code>\u7684\u901f\u5ea6\u5927\u5e45\u63d0\u5347\u3002\u8fd9\u7bc7\u6587\u7ae0\u89e3\u91ca\u4e86\u90e8\u5206\u4ed6\u6240\u505a\u7684\u66f4\u6539\u7684\u7ec6\u8282\uff0c\u8fd9\u4e9b\u6539\u52a8\u4f1a\u5728 V8 7.2 \u7248\u672c\u63d0\u4f9b\u3002<\/p>\n\n\n\n<h2 id=\"%E5%B1%95%E5%BC%80%E5%85%83%E7%B4%A0\">\u5c55\u5f00\u5143\u7d20<\/h2>\n\n\n\n<p>\u5c55\u5f00\u5143\u7d20\u662f\u5177\u6709<code>...iterable<\/code>\u5f62\u5f0f\u7684\u6570\u7ec4\u5b57\u9762\u91cf\u7684\u7ec4\u6210\u3002\u8fd9\u4e00\u7279\u6027\u5728 ES2015 \u4e2d\u63d0\u51fa\uff0c\u4f5c\u4e3a\u4e00\u79cd\u4ece\u53ef\u8fed\u4ee3\u5bf9\u8c61\u521b\u5efa\u6570\u7ec4\u7684\u65b0\u65b9\u5f0f\u3002\u6bd4\u5982\uff0c\u6570\u7ec4\u5b57\u9762\u91cf<code>[1, ...arr, 4, ...b]<\/code>\u4f1a\u521b\u5efa\u4e00\u4e2a\u9996\u5148\u662f<code>1<\/code>\uff0c\u968f\u540e\u662f<code>arr<\/code>\u7684\u5404\u4e2a\u5143\u7d20\uff0c\u5176\u6b21\u662f<code>4<\/code>\uff0c\u6700\u540e\u662f<code>b<\/code>\u7684\u5404\u4e2a\u5143\u7d20\u7684\u6570\u7ec4\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>const a = [2, 3];\nconst b = [5, 6, 7];\nconst result = [1, ...a, 4, ...b];\n\/\/ \u2192 [1, 2, 3, 4, 5, 6, 7]\n<\/code><\/pre>\n\n\n\n<p>\u53e6\u4e00\u4e2a\u4f8b\u5b50\uff0c\u4efb\u4f55\u5b57\u7b26\u4e32\u90fd\u53ef\u4ee5\u5c55\u5f00\u4e3a\u4e00\u4e2a\u5305\u542b\u5176\u6240\u6709\u5b57\u7b26\uff08Unicode \u7801\u4f4d\uff09\u7684\u6570\u7ec4\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>const str = '\u3053\u3093\u306b\u3061\u306f';\nconst result = [...str];\n\/\/ \u2192 ['\u3053', '\u3093', '\u306b', '\u3061', '\u306f']\n<\/code><\/pre>\n\n\n\n<p>\u76f8\u4f3c\u7684\uff0c\u4e00\u4e2a\u96c6\u5408\u4e5f\u53ef\u4ee5\u88ab\u5c55\u5f00\u4e3a\u5b83\u6240\u5305\u542b\u7684\u5143\u7d20\u7684\u6570\u7ec4\uff0c\u6309\u7167\u8fed\u4ee3\u987a\u5e8f\u6392\u5217\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>const s = new Set();\ns.add('V8');\ns.add('TurboFan');\nconst result = [...s];\n\/\/ \u2192 ['V8', 'TurboFan']\n<\/code><\/pre>\n\n\n\n<p>\u603b\u800c\u8a00\u4e4b\uff0c\u6570\u7ec4\u5b57\u9762\u91cf\u4e2d\u7684\u5c55\u5f00\u5143\u7d20\u8bed\u6cd5<code>...x<\/code>\u5047\u5b9a<code>x<\/code>\u63d0\u4f9b\u4e00\u4e2a\u8fed\u4ee3\u5668\uff08\u901a\u8fc7<code>x[Symbol.iterator()]<\/code>\u8bbf\u95ee\u3002\u7136\u540e\u901a\u8fc7\u8be5\u8fed\u4ee3\u5668\u83b7\u53d6\u5143\u7d20\u63d2\u5165\u5230\u7ed3\u679c\u6570\u7ec4\u3002<\/p>\n\n\n\n<p>\u5c06\u6570\u7ec4\u5c55\u5f00\u5230\u4e00\u4e2a\u65b0\u7684\u6570\u7ec4\uff0c\u524d\u540e\u4e0d\u6dfb\u52a0\u5176\u4ed6\u5143\u7d20\u7684\u7b80\u5355\u4f7f\u7528\u60c5\u666f\uff0c\u5373<code>[...arr]<\/code>\uff0c\u88ab\u8ba4\u4e3a\u662f ES2015 \u4e2d\u4e00\u79cd\u7b80\u6d01\u3001\u7ba1\u7528\u7684\u6d45\u62f7\u8d1d\u65b9\u6cd5\u3002\u4e0d\u5e78\u7684\u662f\uff0c\u5728 V8 \u4e2d\uff0c\u8fd9\u4e00\u64cd\u4f5c\u7684\u6027\u80fd\u8fdc\u4f4e\u4e8e ES5 \u4e2d\u7684\u5176\u4ed6\u5199\u6cd5\u3002Hai \u7684\u76ee\u6807\u5c31\u662f\u6539\u53d8\u8fd9\u4e00\u73b0\u72b6\u3002<\/p>\n\n\n\n<h1 id=\"%E4%B8%BA%E4%BB%80%E4%B9%88%E5%B1%95%E5%BC%80%E5%85%83%E7%B4%A0%E4%BB%A5%E5%89%8D%E8%BF%99%E4%B9%88%E6%85%A2\">\u4e3a\u4ec0\u4e48\u5c55\u5f00\u5143\u7d20\uff08\u4ee5\u524d\uff09\u8fd9\u4e48\u6162\uff1f<\/h1>\n\n\n\n<p>\u6709\u8bb8\u591a\u6d45\u62f7\u8d1d\u6570\u7ec4<code>arr<\/code>\u7684\u65b9\u6cd5\u3002\u4f8b\u5982\uff0c\u4f60\u53ef\u4ee5\u4f7f\u7528<code>arr.slice()<\/code>\uff0c\u6216\u8005<code>arr.concat()<\/code>\uff0c\u6216\u8005<code>[...arr]<\/code>\u3002\u6216\u8005\uff0c\u4f60\u53ef\u4ee5\u81ea\u5df1\u5199\u4e00\u4e2a<code>clone<\/code>\u51fd\u6570\uff0c\u901a\u8fc7\u4e00\u4e2a\u6807\u51c6\u7684<code>for<\/code>\u5faa\u73af\u8fdb\u884c\u6d45\u62f7\u8d1d\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>function clone(arr) {\n  \/\/ Pre-allocate the correct number of elements, to avoid\n  \/\/ having to grow the array.\n  const result = new Array(arr.length);\n  for (let i = 0; i &lt; arr.length; i++) {\n    result[i] = arr[i];\n  }\n  return result;\n}\n<\/code><\/pre>\n\n\n\n<p>\u5728\u7406\u60f3\u60c5\u51b5\u4e0b\uff0c\u6240\u6709\u8fd9\u4e9b\u65b9\u6cd5\u5e94\u8be5\u5177\u6709\u63a5\u8fd1\u7684\u6027\u80fd\u3002\u4e0d\u5e78\u7684\u662f\uff0c\u5982\u679c\u4f60\u9009\u62e9\u4e86<code>[...arr]<\/code>\uff0c\u5728 V8 \u4e2d\u5b83\u5c06\u4f1a\u6bd4<code>clone<\/code>\u51fd\u6570\u6162\u3002\u5176\u539f\u56e0\u5728\u4e8e V8 \u5c06<code>[...arr]<\/code>\u8f6c\u8bd1\u4e3a\u7c7b\u4f3c\u8fd9\u6837\u7684\u4ee3\u7801\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>function(arr) {\n  const result = [];\n  const iterator = arr[Symbol.iterator]();\n  const next = iterator.next;\n  for ( ; ; ) {\n    const iteratorResult = next.call(iterator);\n    if (iteratorResult.done) break;\n    result.push(iteratorResult.value);\n  }\n  return result;\n}\n<\/code><\/pre>\n\n\n\n<p>\u8fd9\u6bb5\u4ee3\u7801\u6bd4<code>clone<\/code>\u6162\u7684\u51e0\u4e2a\u4e3b\u8981\u539f\u56e0\u662f\uff1a<\/p>\n\n\n\n<ol><li>\u5b83\u9700\u8981\u5728\u4e00\u5f00\u59cb\u901a\u8fc7\u8bfb\u53d6\u548c\u68c0\u67e5<code>Symbol.interator<\/code>\u5c5e\u6027\u6765\u521b\u5efa\u4e00\u4e2a<code>iterator<\/code>\u3002<\/li><li>\u5b83\u5728\u6bcf\u6b21\u5faa\u73af\u90fd\u8981\u521b\u5efa\u548c\u67e5\u8be2<code>iteratorResult<\/code>\u5bf9\u8c61\u3002<\/li><li>\u5b83\u5728\u6bcf\u6b21\u5faa\u73af\u4e2d\u901a\u8fc7\u8c03\u7528<code>push<\/code>\u589e\u5927<code>result<\/code>\u6570\u7ec4\uff0c\u5bfc\u81f4\u7a7a\u95f4\u7684\u4e0d\u65ad\u91cd\u65b0\u5206\u914d\u3002<\/li><\/ol>\n\n\n\n<p>\u4f7f\u7528\u8fd9\u4e00\u5b9e\u73b0\u7684\u539f\u56e0\u662f\u56e0\u4e3a\uff0c\u6b63\u5982\u4e4b\u524d\u6240\u63d0\u5230\u7684\uff0c\u5c55\u5f00\u624d\u505a\u4e0d\u4ec5\u53ef\u4ee5\u88ab\u7528\u4e8e\u6570\u7ec4\uff0c\u5b9e\u9645\u4e0a\u53ef\u4ee5\u7528\u4e8e\u4efb\u4f55<em>\u53ef\u8fed\u4ee3<\/em>\u5bf9\u8c61\uff0c\u800c\u4e14\u5fc5\u987b\u9075\u5faa<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Iteration_protocols\">\u8fed\u4ee3\u89c4\u8303<\/a>\u3002\u4e0d\u8fc7\uff0cV8 \u5e94\u8be5\u806a\u660e\u5730\u77e5\u9053\u88ab\u5c55\u5f00\u7684\u5bf9\u8c61\u662f\u4e0d\u662f\u4e00\u4e2a\u6570\u7ec4\uff0c\u6765\u5728\u66f4\u5e95\u5c42\u63d0\u53d6\u5143\u7d20\uff0c\u4ece\u800c\uff1a<\/p>\n\n\n\n<ol><li>\u907f\u514d\u521b\u5efa\u8fed\u4ee3\u5668\u5bf9\u8c61<\/li><li>\u907f\u514d\u521b\u5efa\u8fed\u4ee3\u5668\u7ed3\u679c\u5bf9\u8c61<\/li><li>\u907f\u514d\u53cd\u590d\u589e\u957f\u5e76\u91cd\u5206\u914d\u7ed3\u679c\u6570\u7ec4\uff08\u6211\u4eec\u5df2\u7ecf\u63d0\u524d\u77e5\u9053\u5143\u7d20\u7684\u4e2a\u6570\uff09<\/li><\/ol>\n\n\n\n<p>\u6211\u4eec\u5c06\u8fd9\u4e00\u7b80\u5355\u7684\u60f3\u6cd5\u4f7f\u7528<a href=\"https:\/\/v8.js.cn\/blog\/csa\/\">CSA<\/a>\u5b9e\u73b0\uff0c\u9488\u5bf9<em>\u5feb\u901f<\/em>\u6570\u7ec4\uff0c\u4f8b\u5982\u62e5\u6709<a href=\"https:\/\/v8.js.cn\/blog\/elements-kinds\">\u6700\u5e38\u89c1\u7684\u516d\u79cd<\/a>\u5143\u7d20\u7684\u6570\u7ec4\u3002\u8fd9\u4e00\u4f18\u5316\uff0c\u5e94\u7528\u4e8e\u5728\u6570\u7ec4\u5b57\u9762\u91cf\u5f00\u59cb\u4f7f\u7528\u5c55\u5f00\u5bf9\u8c61\u7684<a href=\"https:\/\/v8.js.cn\/blog\/real-world-performance\/\">\u771f\u5b9e\u4e16\u754c\u60c5\u666f<\/a>\uff0c\u4f8b\u5982<code>[...foo]<\/code>\u3002\u5982\u4e0b\u56fe\u6240\u793a\uff0c\u65b0\u7684\u6377\u5f84\u5728\u5c55\u5f00\u4e00\u4e2a\u957f\u5ea6\u4e3a 100,000 \u7684\u6570\u7ec4\u65f6\u62e5\u6709\u83b7\u5f97\u4e86\u4e09\u500d\u7684\u6027\u80fd\u63d0\u5347\uff0c\u6bd4\u624b\u5199\u7684<code>clone<\/code>\u5faa\u73af\u5feb\u4e86 25%\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"http:\/\/ww1.sinaimg.cn\/large\/e985a6f7ly1fy63o78dwlj207g06rwet.jpg\" alt=\"\"\/><\/figure>\n\n\n\n<p>\u6ce8\u610f\uff1a\u867d\u7136\u6ca1\u6709\u5728\u6b64\u663e\u793a\uff0c\u4f46\u662f\u8fd9\u4e00\u6377\u5f84\u540c\u6837\u5bf9\u540e\u8ddf\u5176\u4ed6\u5143\u7d20\u7684\u7528\u6cd5\u6709\u6548\uff08\u4f8b\u5982<code>[...arr, 1, 2, 3]<\/code>\uff0c\u4f46\u524d\u9762\u6709\u5176\u4ed6\u5143\u7d20\u65e0\u6548\uff08\u4f8b\u5982<code>[1, 2, 3, ...arr]<\/code>\uff09\u3002<\/p>\n\n\n\n<h2 id=\"%E4%BB%94%E7%BB%86%E6%A3%80%E6%9F%A5%E8%BF%99%E4%B8%80%E6%8D%B7%E5%BE%84\">\u4ed4\u7ec6\u68c0\u67e5\u8fd9\u4e00\u6377\u5f84<\/h2>\n\n\n\n<p>\u8fd9\u4e00\u65b9\u6cd5\u662f\u4ee4\u4eba\u5fc3\u52a8\u7684\u901f\u5ea6\u63d0\u5347\uff0c\u4f46\u662f\u6211\u4eec\u5fc5\u987b\u4ed4\u7ec6\u4f7f\u7528\u8fd9\u4e00\u6377\u5f84\u662f\u5426\u6b63\u786e\uff1aJavaScript \u5141\u8bb8\u7a0b\u5e8f\u5458\u4ee5\u591a\u79cd\u65b9\u6cd5\u4fee\u6539\u5bf9\u8c61\uff08\u751a\u81f3\u6570\u7ec4\uff09\u7684\u8fed\u4ee3\u8868\u73b0\u3002\u7531\u4e8e\u5c55\u5f00\u5143\u7d20\u4f7f\u7528\u8fed\u4ee3\u89c4\u8303\uff0c\u6211\u4eec\u901a\u8fc7\u5728\u539f\u59cb\u8fed\u4ee3\u673a\u5236\u88ab\u4fee\u6539\u65f6\u4e0d\u4f7f\u7528\u6377\u5f84\u6765\u786e\u4fdd\u8fd9\u4e00\u4fee\u6539\u7b26\u5408\u89c4\u8303\u3002\u4f8b\u5982\u4ee5\u4e0b\u60c5\u666f\uff1a<\/p>\n\n\n\n<h3 id=\"%E8%87%AA%E8%BA%AB%E7%9A%84symboliterator%E5%B1%9E%E6%80%A7\">\u81ea\u8eab\u7684<code>Symbol.iterator<\/code>\u5c5e\u6027<\/h3>\n\n\n\n<p>\u4e00\u822c\u6765\u8bf4\u4e00\u4e2a\u6570\u7ec4<code>arr<\/code>\u4e0d\u4f1a\u62e5\u6709\u5b83\u81ea\u5df1\u7684<code>Symbol.iterator<\/code>\u5c5e\u6027\uff0c\u6240\u4ee5\u5f53\u6211\u4eec\u67e5\u627e\u8be5 symbol \u65f6\u4f1a\u5728\u6570\u7ec4\u7684\u539f\u578b\u4e0a\u627e\u5230\u3002\u4e0b\u65b9\u7684\u4f8b\u5b50\u4e2d\uff0c\u901a\u8fc7\u76f4\u63a5\u5728<code>arr<\/code>\u4e0a\u5b9a\u4e49<code>Symbol.iterator<\/code>\u7ed5\u8fc7\u4e86\u539f\u578b\u3002\u5728\u505a\u8fd9\u6837\u7684\u4fee\u6539\u4e4b\u540e\uff0c\u5728<code>arr<\/code>\u4e0a\u67e5\u627e<code>Symbol.iterator<\/code>\u4f1a\u5f97\u5230\u4e00\u4e2a\u7a7a\u8fed\u4ee3\u5668\uff0c\u6240\u4ee5\u5c55\u5f00<code>arr<\/code>\u4e0d\u4f1a\u83b7\u5f97\u5143\u7d20\uff0c\u5c55\u5f00\u7684\u6570\u7ec4\u5b57\u9762\u91cf\u4f1a\u662f\u4e00\u4e2a\u7a7a\u6570\u7ec4\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>const arr = [1, 2, 3];\narr[Symbol.iterator] = function() {\n  return { next: function() { return { done: true }; } };\n};\nconst result = [...arr];\n\/\/ \u2192 []\n<\/code><\/pre>\n\n\n\n<h3 id=\"%E4%BF%AE%E6%94%B9%E8%BF%87%E7%9A%84-arrayiteratorprototype\">\u4fee\u6539\u8fc7\u7684&nbsp;<code>%ArrayIteratorPrototype%<\/code><\/h3>\n\n\n\n<p><code>next<\/code>\u65b9\u6cd5\u4e5f\u53ef\u4ee5\u76f4\u63a5\u901a\u8fc7<a href=\"https:\/\/tc39.github.io\/ecma262\/#sec-%25arrayiteratorprototype%25-object\"><code>%ArrayIteratorPrototype%<\/code><\/a>\u6765\u4fee\u6539\uff0c\u8fd9\u662f\u6570\u7ec4\u8fed\u4ee3\u5668\u7684\u539f\u578b\uff08\u4f1a\u5f71\u54cd\u6240\u6709\u6570\u7ec4\uff09\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Object.getPrototypeOf([][Symbol.iterator]()).next = function() {\n  return { done: true };\n}\nconst arr = [1, 2, 3];\nconst result = [...arr];\n\/\/ \u2192 []\n<\/code><\/pre>\n\n\n\n<h2 id=\"%E5%A4%84%E7%90%86%E7%A8%80%E7%96%8F%E6%95%B0%E7%BB%84\">\u5904\u7406\u7a00\u758f\u6570\u7ec4<\/h2>\n\n\n\n<p>\u53e6\u4e00\u9700\u8981\u6ce8\u610f\u7684\u70b9\u662f\u590d\u5236\u7a00\u758f\u6570\u7ec4\uff08\u4f8b\u5982<code>['a', , 'c']<\/code>\uff09\u8fd9\u6837\u7f3a\u5931\u90e8\u5206\u5143\u7d20\u7684\u6570\u7ec4\u3002\u5c55\u5f00\u8fd9\u6837\u7684\u6570\u7ec4\uff0c\u7531\u4e8e\u9075\u5b88\u8fed\u4ee3\u89c4\u8303\uff0c\u5c55\u5f00\u8fd9\u6837\u7684\u6570\u7ec4\u4e0d\u4f1a\u4fdd\u7559\u7a7a\u6d1e\uff0c\u800c\u662f\u7528\u76f8\u5e94\u7d22\u5f15\u5904\u7684\u6570\u7ec4\u539f\u578b\u4e2d\u7684\u503c\u586b\u5145\u5b83\u4eec\u3002\u9ed8\u8ba4\u60c5\u51b5\u4e0b\u6570\u7ec4\u7684\u539f\u578b\u4e2d\u6ca1\u6709\u5143\u7d20\uff0c\u610f\u5473\u7740\u7a7a\u6d1e\u5c06\u4f1a\u88ab<code>undefined<\/code>\u586b\u5145\u3002\u4f8b\u5982\uff0c<code>[...['a', , 'c']]<\/code>\u5c06\u4f1a\u83b7\u5f97<code>['a', undefined, 'c']<\/code>\u3002<\/p>\n\n\n\n<p>\u6211\u4eec\u7684\u6377\u5f84\u5728\u8fd9\u79cd\u9ed8\u8ba4\u60c5\u666f\u4e0b\u8db3\u591f\u806a\u660e\u6765\u5904\u7406\u7a7a\u6d1e\u3002\u5b83\u4e0d\u4f1a\u76f2\u76ee\u5730\u590d\u5236\u8f93\u5165\u6570\u7ec4\u7684\u5b58\u50a8\u7a7a\u95f4\uff0c\u800c\u662f\u4f1a\u76d1\u89c6\u8fd9\u4e9b\u7a7a\u6d1e\u5e76\u628a\u5b83\u4eec\u5c0f\u5fc3\u7684\u8f6c\u6362\u6210<code>undefined<\/code>\u503c\u3002\u4e0b\u56fe\u5c55\u793a\u4e86\u5c55\u5f00\u4e00\u4e2a\u6709 100,000 \u4e2a\u5143\u7d20\u4f46\u53ea\u6709 600 \u4e2a\u6574\u6570\u5176\u4ed6\u5747\u662f\u7a7a\u6d1e\u7684\u6570\u7ec4\u7684\u6027\u80fd\u3002\u5c55\u5f00\u8fd9\u6837\u4e00\u4e2a\u5145\u6ee1\u7a7a\u6d1e\u7684\u7a00\u758f\u6570\u7ec4\u73b0\u5728\u6bd4<code>clone<\/code>\u51fd\u6570\u5feb\u56db\u500d\u3002\uff08\u5b83\u4eec\u8fc7\u53bb\u7684\u6027\u80fd\u5927\u81f4\u76f8\u540c\uff0c\u4f46\u5728\u56fe\u4e2d\u672a\u663e\u793a\uff09\u3002<\/p>\n\n\n\n<p>\u6ce8\u610f\uff0c\u867d\u7136\u56fe\u4e2d\u5305\u542b\u4e86<code>slice<\/code>\u65b9\u6cd5\u7684\u7ed3\u679c\uff0c\u4f46\u662f\u4e0e\u5b83\u6bd4\u8f83\u662f\u4e0d\u516c\u5e73\u7684\u56e0\u4e3a<code>slice<\/code>\u5bf9\u7a00\u758f\u6570\u7ec4\u62e5\u6709\u4e0d\u540c\u7684\u8bed\u4e49\uff0c\u5b83\u4f1a\u4fdd\u7559\u6240\u6709\u7684\u7a7a\u6d1e\uff0c\u6240\u4ee5\u5c11\u505a\u4e86\u5f88\u591a\u5de5\u4f5c\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"http:\/\/ww1.sinaimg.cn\/large\/e985a6f7ly1fy64czvhqkj207w06y3yq.jpg\" alt=\"\"\/><\/figure>\n\n\n\n<p>\u6211\u4eec\u7684\u6377\u5f84\u5fc5\u987b\u628a\u7a7a\u6d1e\u586b\u5145\u4e3a<code>undefined<\/code>\uff0c\u8fd9\u4e00\u64cd\u4f5c\u5e76\u4e0d\u8ddf\u5b83\u542c\u8d77\u6765\u4e00\u6837\u7b80\u5355\uff1a\u4ed6\u53ef\u80fd\u9700\u8981\u628a\u6574\u4e2a\u6570\u7ec4\u8f6c\u6362\u6210\u53e6\u4e00\u79cd\u5143\u7d20\u7c7b\u578b\u3002\u4e0b\u4e00\u5f20\u56fe\u7247\u5ea6\u91cf\u4e86\u8fd9\u79cd\u60c5\u666f\u3002\u521d\u59cb\u5316\u548c\u524d\u6587\u4e00\u6837\uff0c\u9664\u4e86\u8fd9\u4e00\u6b21\u6211\u4eec\u7684 600 \u4e2a\u6570\u7ec4\u5143\u7d20\u662f\u672a\u62c6\u5c01\u7684 double \u7c7b\u578b\uff0c\u6570\u7ec4\u7684\u5143\u7d20\u7c7b\u578b\u662f<a href=\"https:\/\/v8.js.cn\/blog\/elements-kinds\/\"><code>HOLEY_DOUBLE_ELEMENTS<\/code><\/a>\u3002\u56e0\u4e3a\u8fd9\u4e00\u5143\u7d20\u7c7b\u578b\u65e0\u6cd5\u627f\u8f7d\u7c7b\u4f3c<code>undefined<\/code>\u7684\u6807\u8bb0\u503c\uff0c\u5c55\u5f00\u8fd9\u4e00\u6570\u7ec4\u9700\u8981\u6267\u884c\u4ee3\u4ef7\u9ad8\u6602\u7684\u5143\u7d20\u7c7b\u578b\u8f6c\u6362\uff0c\u8fd9\u5c31\u662f\u4e3a\u4ec0\u4e48<code>[...a]<\/code>\u7684\u5206\u6570\u6bd4\u4e0a\u4e00\u5f20\u56fe\u4f4e\u8bb8\u591a\u3002\u4e0d\u8fc7\uff0c\u8fd8\u662f\u6bd4<code>clone(a)<\/code>\u8981\u5feb\u8bb8\u591a\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"http:\/\/ww1.sinaimg.cn\/large\/e985a6f7ly1fy64pq2oj8j207u06qwet.jpg\" alt=\"\"\/><\/figure>\n\n\n\n<h2 id=\"%E5%B1%95%E5%BC%80%E5%AD%97%E7%AC%A6%E4%B8%B2%E9%9B%86%E5%90%88%E4%BB%A5%E5%8F%8A%E6%98%A0%E5%B0%84\">\u5c55\u5f00\u5b57\u7b26\u4e32\u3001\u96c6\u5408\u4ee5\u53ca\u6620\u5c04<\/h2>\n\n\n\n<p>\u8df3\u8fc7\u8fed\u4ee3\u5668\u5bf9\u8c61\u5e76\u907f\u514d\u589e\u957f\u7ed3\u679c\u6570\u7ec4\u7684\u60f3\u6cd5\u540c\u6837\u9002\u7528\u4e8e\u4f20\u64ad\u5176\u4ed6\u6807\u51c6\u6570\u636e\u7c7b\u578b\u3002\u5b9e\u9645\u4e0a\uff0c\u6211\u4eec\u4e3a\u539f\u59cb\u5b57\u7b26\u4e32\uff0c\u96c6\u5408\u548c\u6620\u5c04\u5b9e\u73b0\u4e86\u7c7b\u4f3c\u7684\u5feb\u901f\u8def\u5f84\uff0c\u6bcf\u6b21\u5728\u5b58\u5728\u4fee\u6539\u7684\u8fed\u4ee3\u884c\u4e3a\u65f6\u90fd\u8981\u5c0f\u5fc3\u5730\u7ed5\u8fc7\u5b83\u4eec\u3002<\/p>\n\n\n\n<p>\u5173\u4e8e\u96c6\u5408\uff0c\u8fd9\u4e00\u6377\u5f84\u4e0d\u4ec5\u652f\u6301\u76f4\u63a5\u5c55\u5f00\u4e00\u4e2a\u96c6\u5408\uff08<code>[...set]<\/code>\uff09\uff0c\u8fd8\u652f\u6301\u5c55\u5f00\u5b83\u7684\u952e\u8fed\u4ee3\u5668\uff08<code>[...set.keys()]<\/code>\uff09\u548c\u4ed6\u7684\u503c\u8fed\u4ee3\u5668\uff08<code>[...set.values()]<\/code>\uff09\u3002\u5728\u6211\u4eec\u7684\u5fae\u57fa\u51c6\u6d4b\u8bd5\u4e2d\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u73b0\u5728\u6bd4\u4ee5\u524d\u5feb\u4e86 18 \u500d\u3002<\/p>\n\n\n\n<p>\u5bf9\u4e8e\u6620\u5c04\u7684\u6377\u5f84\u4e5f\u662f\u7c7b\u4f3c\u7684\uff0c\u4f46\u662f\u5e76\u4e0d\u652f\u6301\u76f4\u63a5\u5c55\u5f00\u4e00\u4e2a\u6620\u5c04\uff08<code>[...map]<\/code>\uff09\uff0c\u56e0\u4e3a\u6211\u4eec\u8ba4\u4e3a\u8fd9\u662f\u4e00\u4e2a\u4e0d\u5e38\u7528\u7684\u64cd\u4f5c\u3002\u7531\u4e8e\u67d0\u4e9b\u539f\u56e0\uff0c\u8fd9\u4e00\u6377\u5f84\u4e5f\u4e0d\u652f\u6301<code>.entries()<\/code>\u8fed\u4ee3\u5668\u3002\u5728\u6211\u4eec\u7684\u5fae\u57fa\u51c6\u6d4b\u8bd5\u4e2d\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u73b0\u5728\u6bd4\u4ee5\u524d\u5feb\u4e86\u5927\u7ea614\u500d\u3002<\/p>\n\n\n\n<p>\u5bf9\u4e8e\u5c55\u5f00\u5b57\u7b26\u4e32\uff08<code>[...string]<\/code>\uff09\uff0c\u6211\u4eec\u6d4b\u5f97\u4e86\u5927\u7ea6\u4e94\u500d\u7684\u6027\u80fd\u63d0\u5347\uff0c\u5728\u4e0b\u56fe\u4e2d\u4ee5\u7d2b\u8272\u548c\u7eff\u8272\u7ebf\u6761\u8868\u793a\u3002\u6ce8\u610f\uff0c\u8fd9\u751a\u81f3\u6bd4\u5728\u4e0b\u56fe\u4e2d\u4ee5\u84dd\u8272\u548c\u7c89\u8272\u663e\u793a\u7684 TurboFan \u4f18\u5316\u7684 for-of \u5faa\u73af\u8981\u5feb\u3002\uff08TurboFan \u53ef\u4ee5\u7406\u89e3\u5b57\u7b26\u4e32\u8fed\u4ee3\u5e76\u4e3a\u5176\u751f\u6210\u4f18\u5316\u540e\u7684\u4ee3\u7801\uff09\u3002\u5728\u6bcf\u79cd\u60c5\u51b5\u4e0b\u5177\u6709\u4e24\u4e2a\u56fe\u6807\u7684\u539f\u56e0\u662f\u5fae\u57fa\u51c6\u6d4b\u8bd5\u5728\u5728\u4e24\u4e2a\u4e0d\u540c\u7684\u5b57\u7b26\u4e32\u8868\u793a\u4e0a\u64cd\u4f5c\uff08\u5355\u5b57\u8282\u5b57\u7b26\u4e32\u548c\u53cc\u5b57\u8282\u5b57\u7b26\u4e32\uff09\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"http:\/\/ww1.sinaimg.cn\/large\/e985a6f7ly1fy64z730tqj209w06w751.jpg\" alt=\"\"\/><\/figure>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"http:\/\/ww1.sinaimg.cn\/large\/e985a6f7ly1fy64zcsilej208p06wjrk.jpg\" alt=\"\"\/><\/figure>\n\n\n\n<h2 id=\"%E6%8F%90%E5%8D%87arrayform%E7%9A%84%E6%80%A7%E8%83%BD\">\u63d0\u5347<code>Array.form<\/code>\u7684\u6027\u80fd<\/h2>\n\n\n\n<p>\u5e78\u8fd0\u7684\u662f\uff0c\u6211\u4eec\u7684\u5c55\u5f00\u5143\u7d20\u7684\u6377\u5f84\u540c\u6837\u53ef\u4ee5\u91cd\u7528\u4e8e<code>Array.from<\/code>\uff0c\u53ea\u8981\u4f20\u5165<code>Array.from<\/code>\u7684\u662f\u4e00\u4e2a\u53ef\u8fed\u4ee3\u5bf9\u8c61\u5e76\u4e14\u4e0d\u5305\u542b\u6620\u5c04\u51fd\u6570\u3002\uff08\u4f8b\u5982<code>Array.from([1, 2, 3])<\/code>\uff09\u3002\u53ef\u4ee5\u91cd\u7528\u7684\u539f\u56e0\u662f\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c<code>Array.from<\/code>\u7684\u8868\u73b0\u4e0e\u5c55\u5f00\u64cd\u4f5c\u4e00\u81f4\u3002\u5b83\u5bfc\u81f4\u4e86\u5de8\u5927\u7684\u6027\u80fd\u63d0\u5347\uff0c\u5982\u4e0b\u6240\u793a\uff0c\u5bf9\u4e8e\u5177\u6709100\u4e2a\u53cc\u7cbe\u5ea6\u6570\u7684\u6570\u7ec4\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"http:\/\/ww1.sinaimg.cn\/large\/e985a6f7ly1fy652r5exwj207w06qmxc.jpg\" alt=\"\"\/><\/figure>\n\n\n\n<h2 id=\"%E7%BB%93%E8%AE%BA\">\u7ed3\u8bba<\/h2>\n\n\n\n<p>V8 v7.2 \/ Chrome 72 \u5927\u5e45\u63d0\u5347\u4e86\u5c55\u5f00\u5143\u7d20\u7684\u6027\u80fd\uff0c\u5f53\u4ed6\u4eec\u5728\u6570\u7ec4\u5b57\u9762\u91cf\u7684\u6700\u524d\u4f7f\u7528\uff0c\u4f8b\u5982<code>[...x]<\/code>\u6216\u8005<code>[...x, 1, 2]<\/code>\u3002\u8fd9\u4e00\u63d0\u5347\u5e94\u7528\u4e8e\u5c55\u5f00\u6570\u7ec4\u3001\u539f\u59cb\u5b57\u7b26\u4e32\u3001\u6620\u5c04\u7684\u952e\u3001\u6620\u5c04\u7684\u503c\uff0c\u4ee5\u53ca<code>Array.from(x)<\/code>\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Speeding up spread elements \u539f\u6587&nbsp;https:\/\/v8.dev\/blog &hellip; <\/p>\n<p class=\"link-more\"><a href=\"https:\/\/sora.sound.moe\/?p=774\" class=\"more-link\">\u7ee7\u7eed\u9605\u8bfb<span class=\"screen-reader-text\">\u201c[\u7ffb\u8bd1] \u52a0\u901f\u5c55\u5f00\u5143\u7d20\u201d<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[2],"tags":[],"uagb_featured_image_src":{"full":false,"thumbnail":false,"medium":false,"medium_large":false,"large":false,"1536x1536":false,"2048x2048":false,"twentyseventeen-featured-image":false,"twentyseventeen-thumbnail-avatar":false},"uagb_author_info":{"display_name":"Sora","author_link":"https:\/\/sora.sound.moe\/?author=1"},"uagb_comment_info":0,"uagb_excerpt":"Speeding up spread elements \u539f\u6587&nbsp;https:\/\/v8.dev\/blog&hellip;","_links":{"self":[{"href":"https:\/\/sora.sound.moe\/index.php?rest_route=\/wp\/v2\/posts\/774"}],"collection":[{"href":"https:\/\/sora.sound.moe\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/sora.sound.moe\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/sora.sound.moe\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/sora.sound.moe\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=774"}],"version-history":[{"count":0,"href":"https:\/\/sora.sound.moe\/index.php?rest_route=\/wp\/v2\/posts\/774\/revisions"}],"wp:attachment":[{"href":"https:\/\/sora.sound.moe\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=774"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/sora.sound.moe\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=774"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/sora.sound.moe\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=774"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}