{"id":1795,"date":"2023-03-21T23:24:03","date_gmt":"2023-03-21T15:24:03","guid":{"rendered":"https:\/\/zhuxinyong.com\/?p=1795"},"modified":"2023-03-21T23:51:50","modified_gmt":"2023-03-21T15:51:50","slug":"javascript-ke-shi-hua-zuo-yong-yu-lian","status":"publish","type":"post","link":"https:\/\/zhuxinyong.com\/?p=1795","title":{"rendered":"JavaScript \u53ef\u89c6\u5316\uff1a\u4f5c\u7528\u57df\uff08\u94fe\uff09"},"content":{"rendered":"

\"\"<\/p>\n

\u539f\u6587\u5730\u5740\uff1ahttps:\/\/dev.to\/lydiahallie\/javascript-visualized-scope-chain-13pd<\/a><\/p>\n

\u662f\u65f6\u5019\u8c08\u4e00\u8c08\u4f5c\u7528\u57df\u94fe\u4e86\ud83d\udd7a\ud83c\udffc \u5728\u8fd9\u7bc7\u6587\u7ae0\u4e2d\uff0c\u6211\u5047\u8bbe\u60a8\u4e86\u89e3\u4e00\u4e9b\u6267\u884c\u4e0a\u4e0b\u6587\u7684\u57fa\u7840\u77e5\u8bc6\uff1a\u4e0d\u8fc7\u6211\u5f88\u5feb\u4e5f\u4f1a\u5199\u4e00\u7bc7\u5173\u4e8e\u5b83\u7684\u6587\u7ae0\ud83d\ude03<\/p>\n

\u8ba9\u6211\u4eec\u770b\u4e00\u4e0b\u4e0b\u9762\u7684\u4ee3\u7801\uff1a<\/p>\n

const name = "Lydia"\nconst age = 21\nconst city = "San Francisco"\n\nfunction getPersonInfo() {\n  const name = "Sarah"\n  const age = 22\n\n  return `${name} is ${age} and lives in ${city}`\n}\n\nconsole.log(getPersonInfo())\n<\/code><\/pre>\n
\u6211\u4eec\u6b63\u5728\u8c03\u7528 getPersonInfo \u51fd\u6570\uff0c\u5b83\u8fd4\u56de\u4e00\u4e2a\u5305\u542b name \u3001 age \u548c city \u53d8\u91cf\u503c\u7684\u5b57\u7b26\u4e32\uff1a<\/p>\n
Sarah is 22 and lives in San Francisco <\/code>\u3002\u4f46\u662f\uff0c getPersonInfo<\/code> \u51fd\u6570\u4e0d\u5305\u542b\u540d\u4e3a city<\/code> \ud83e\udd28 \u7684\u53d8\u91cf\uff1f\u5b83\u662f\u5982\u4f55\u77e5\u9053 city \u7684\u503c\u7684\uff1f<\/p>\n
\u9996\u5148\uff0c\u4e3a\u4e0d\u540c\u7684\u4e0a\u4e0b\u6587\u8bbe\u7f6e\u5185\u5b58\u7a7a\u95f4\u3002\u6211\u4eec\u6709\u9ed8\u8ba4\u7684\u5168\u5c40\u4e0a\u4e0b\u6587\uff08\u5728\u6d4f\u89c8\u5668\u4e2d\u4e3a window<\/code> \uff0c\u5728 Node \u4e2d\u4e3a global<\/code> \uff09\uff0c\u4ee5\u53ca\u5df2\u8c03\u7528\u7684 getPersonInfo<\/code> \u51fd\u6570\u7684\u5c40\u90e8\u4e0a\u4e0b\u6587\u3002\u6bcf\u4e2a\u4e0a\u4e0b\u6587\u4e5f\u6709\u4e00\u4e2a\u4f5c\u7528\u57df\u94fe\u3002<\/p>\n
\u5bf9\u4e8e getPersonInfo<\/code> \u51fd\u6570\uff0c\u4f5c\u7528\u57df\u94fe\u770b\u8d77\u6765\u50cf\u8fd9\u6837\uff08\u522b\u62c5\u5fc3\uff0c\u5b83\u73b0\u5728\u8fd8\u6ca1\u6709\u610f\u4e49\uff09\uff1a<\/p>\n
\"\"<\/p>\n
\u4f5c\u7528\u57df\u94fe\u57fa\u672c\u4e0a\u662f\u4e00\u4e2a\u5bf9\u8c61\u7684 "\u5f15\u7528\u94fe"\uff0c\u5b83\u5305\u542b\u5bf9\u8be5\u6267\u884c\u4e0a\u4e0b\u6587\u4e2d\u53ef\u5f15\u7528\u7684\u503c\uff08\u548c\u5176\u4ed6\u4f5c\u7528\u57df\uff09\u7684\u5f15\u7528\u3002(\u26d3: "\u563f\uff0c\u8fd9\u4e9b\u662f\u4f60\u53ef\u4ee5\u4ece\u8fd9\u4e2a\u4e0a\u4e0b\u6587\u4e2d\u5f15\u7528\u7684\u6240\u6709\u503c"\uff09\u3002\u5f53\u6267\u884c\u4e0a\u4e0b\u6587\u88ab\u521b\u5efa\u65f6\uff0c\u4f5c\u7528\u57df\u94fe\u5c31\u88ab\u521b\u5efa\u4e86\uff0c\u4e5f\u5c31\u662f\u8bf4\uff0c\u5b83\u662f\u5728\u8fd0\u884c\u65f6\u88ab\u521b\u5efa\u7684\u3002<\/p>\n
\u7136\u800c\uff0c\u5728\u672c\u7bc7\u6587\u7ae0\u4e2d\u6211\u4e0d\u4f1a\u8c08\u8bba\u6d3b\u52a8\u5bf9\u8c61\u6216\u6267\u884c\u4e0a\u4e0b\u6587\u7684\u6982\u5ff5\uff0c\u6211\u4eec\u53ea\u9700\u8981\u5173\u6ce8\u4f5c\u7528\u57df\uff01\u5728\u4ee5\u4e0b\u793a\u4f8b\u4e2d\uff0c\u6267\u884c\u4e0a\u4e0b\u6587\u4e2d\u7684\u952e\/\u503c\u5bf9\u8868\u793a\u4f5c\u7528\u57df\u94fe\u5bf9\u53d8\u91cf\u7684\u5f15\u7528\u3002<\/p>\n
\"\"<\/p>\n
\u5168\u5c40\u6267\u884c\u4e0a\u4e0b\u6587\u7684\u4f5c\u7528\u57df\u94fe\u5f15\u7528\u4e86 3 \u4e2a\u53d8\u91cf\uff1a name<\/code> \u7684\u503c\u4e3a Lydia<\/code> \uff0c age<\/code> \u7684\u503c\u4e3a 21<\/code> \uff0c city<\/code> \u7684\u503c\u4e3a San Francisco<\/code> \u3002\u5728\u672c\u5730\u4e0a\u4e0b\u6587\u4e2d\uff0c\u6211\u4eec\u5f15\u7528\u4e86 2 \u4e2a\u53d8\u91cf\uff1a name<\/code> \u7684\u503c\u4e3a Sarah<\/code> \uff0c age<\/code> \u7684\u503c\u4e3a 22<\/code> \u3002<\/p>\n
\u5f53\u6211\u4eec\u5c1d\u8bd5\u8bbf\u95ee getPersonInfo<\/code> \u51fd\u6570\u4e2d\u7684\u53d8\u91cf\u65f6\uff0c\u5f15\u64ce\u9996\u5148\u68c0\u67e5\u5c40\u90e8\u4f5c\u7528\u57df\u94fe\u3002<\/p>\n
\"1\"<\/p>\n
\u672c\u5730\u4f5c\u7528\u57df\u94fe\u5f15\u7528\u4e86 name<\/code> \u548c age<\/code> \uff01 name<\/code> \u7684\u503c\u4e3a Sarah<\/code> \u800c age<\/code> \u7684\u503c\u4e3a 22<\/code> \u3002\u4f46\u662f\u73b0\u5728\uff0c\u5f53\u5b83\u5c1d\u8bd5\u8bbf\u95ee city<\/code> \u65f6\u4f1a\u53d1\u751f\u4ec0\u4e48\uff1f<\/p>\n
\u4e3a\u4e86\u627e\u5230city\u7684\u503c\uff0c\u5f15\u64ce "\u6cbf\u7740\u4f5c\u7528\u57df\u94fe\u5411\u4e0b\u8d70"\u3002\u8fd9\u57fa\u672c\u4e0a\u610f\u5473\u7740\u5f15\u64ce\u4e0d\u4f1a\u8f7b\u6613\u653e\u5f03\uff1a\u5b83\u4e3a\u4f60\u52aa\u529b\u5de5\u4f5c\uff0c\u770b\u662f\u5426\u80fd\u5728\u672c\u5730\u4f5c\u7528\u57df\u6709\u4e00\u4e2a\u5f15\u7528\u7684\u5916\u90e8\u4f5c\u7528\u57df\u4e2d\u627e\u5230\u53d8\u91cfcity\u7684\u503c\uff0c\u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\u5c31\u662f\u5168\u5c40\u5bf9\u8c61\u3002<\/p>\n
\"2\"<\/p>\n
\u5728\u5168\u5c40\u4e0a\u4e0b\u6587\u4e2d\uff0c\u6211\u4eec\u58f0\u660e\u53d8\u91cf city<\/code> \u7684\u503c\u4e3a San Francisco<\/code> \uff0c\u56e0\u6b64\u5f15\u7528\u4e86\u53d8\u91cf city<\/code> \u3002\u73b0\u5728\u6211\u4eec\u6709\u4e86\u53d8\u91cf\u7684\u503c\uff0c\u51fd\u6570 getPersonInfo<\/code> \u53ef\u4ee5\u8fd4\u56de\u5b57\u7b26\u4e32 Sarah is 22 and lives in San Francisco<\/code> \ud83c\udf89<\/p>\n
\u6211\u4eec\u53ef\u4ee5\u6cbf\u7740\u4f5c\u7528\u57df\u94fe\u5f80\u4e0b\u8d70\uff0c\u4f46\u6211\u4eec\u4e0d\u80fd\u6cbf\u7740\u4f5c\u7528\u57df\u94fe\u5f80\u4e0a\u8d70\u3002 \uff08\u597d\u5427\uff0c\u8fd9\u53ef\u80fd\u4f1a\u8ba9\u4eba\u611f\u5230\u56f0\u60d1\uff0c\u56e0\u4e3a\u6709\u4e9b\u4eba\u8bf4\u5411\u4e0a\u800c\u4e0d\u662f\u5411\u4e0b\uff0c\u6240\u4ee5\u6211\u6539\u4e00\u4e0b\uff1a\u4f60\u53ef\u4ee5\u53bb\u5916\u90e8\u7684\u4f5c\u7528\u57df\uff0c\u4f46\u4e0d\u80fd\u53bb\u66f4\u5185\u90e8\u7684……\uff08\u5185\u90e8\u7684……\uff1f\uff09\u4f5c\u7528\u57df\u3002\u6211\u559c\u6b22\u628a\u8fd9\u60f3\u8c61\u6210\u4e00\u79cd\u7011\u5e03\u3002<\/p>\n
\"\"<\/p>\n
\u751a\u81f3\u66f4\u6df1\uff1a<\/p>\n
\"\"<\/p>\n
\u6211\u4eec\u4ee5\u8fd9\u6bb5\u4ee3\u7801\u4e3a\u4f8b\u3002<\/p>\n
\"\"<\/p>\n
\u5b83\u51e0\u4e4e\u662f\u4e00\u6837\u7684\uff0c\u4f46\u662f\u6709\u4e00\u4e2a\u5f88\u5927\u7684\u4e0d\u540c\uff1a\u6211\u4eec\u73b0\u5728\u53ea\u5728 getPersonInfo<\/code> \u51fd\u6570\u4e2d\u58f0\u660e\u4e86 city<\/code> \uff0c\u800c\u4e0d\u662f\u5728\u5168\u5c40\u8303\u56f4\u5185\u3002\u6211\u4eec\u6ca1\u6709\u8c03\u7528 getPersonInfo<\/code> \u51fd\u6570\uff0c\u56e0\u6b64\u4e5f\u6ca1\u6709\u521b\u5efa\u672c\u5730\u4e0a\u4e0b\u6587\u3002\u7136\u800c\uff0c\u6211\u4eec\u5c1d\u8bd5\u5728\u5168\u5c40\u4e0a\u4e0b\u6587\u4e2d\u8bbf\u95ee name<\/code> \u3001 age<\/code> \u548c city<\/code> \u7684\u503c\u3002<\/p>\n
\"3\"<\/p>\n
\u5b83\u629b\u51fa\u4e00\u4e2a ReferenceError<\/code> \uff01\u5b83\u65e0\u6cd5\u5728\u5168\u5c40\u4f5c\u7528\u57df\u4e2d\u627e\u5230\u5bf9\u540d\u4e3a city<\/code> \u7684\u53d8\u91cf\u7684\u5f15\u7528\uff0c\u5e76\u4e14\u6ca1\u6709\u8981\u67e5\u627e\u7684\u5916\u90e8\u4f5c\u7528\u57df\uff0c\u5b83\u4e5f\u65e0\u6cd5\u5728\u4f5c\u7528\u57df\u94fe\u4e2d\u5411\u4e0a\u79fb\u52a8\u3002<\/p>\n
\u8fd9\u6837\uff0c\u60a8\u53ef\u4ee5\u4f7f\u7528\u4f5c\u7528\u57df\u4f5c\u4e3a\u4e00\u79cd\u201c\u4fdd\u62a4\u201d\u60a8\u7684\u53d8\u91cf\u5e76\u91cd\u590d\u4f7f\u7528\u53d8\u91cf\u540d\u79f0\u7684\u65b9\u6cd5\u3002<\/p>\n
\u9664\u4e86\u5168\u5c40\u548c\u5c40\u90e8\u4f5c\u7528\u57df\u4e4b\u5916\uff0c\u8fd8\u6709\u4e00\u4e2a\u5757\u4f5c\u7528\u57df\u3002\u4f7f\u7528 let<\/code> \u6216 const <\/code>\u5173\u952e\u5b57\u58f0\u660e\u7684\u53d8\u91cf\u7684\u8303\u56f4\u9650\u5b9a\u4e3a\u6700\u8fd1\u7684\u5927\u62ec\u53f7 ( { }<\/code> )\u3002<\/p>\n
const age = 21\n\nfunction checkAge() {\n  if (age < 21) {\n    const message = "You cannot drink!"\n    return message\n  } else {\n    const message = "You can drink!"\n    return message\n  }\n} \n<\/code><\/pre>\n
\u60a8\u53ef\u4ee5\u5c06\u8303\u56f4\u53ef\u89c6\u5316\u4e3a\uff1a<\/p>\n
\"\"<\/p>\n
\u6211\u4eec\u6709\u4e00\u4e2a\u5168\u5c40\u4f5c\u7528\u57df\u3001\u4e00\u4e2a\u51fd\u6570\u4f5c\u7528\u57df\u548c\u4e24\u4e2a\u5757\u7ea7\u4f5c\u7528\u57df\u3002\u6211\u4eec\u80fd\u591f\u4e24\u6b21\u58f0\u660e\u53d8\u91cf message<\/code> \uff0c\u56e0\u4e3a\u53d8\u91cf\u7684\u8303\u56f4\u9650\u5b9a\u5728\u5927\u62ec\u53f7\u5185\u3002<\/p>\n
\u5feb\u901f\u56de\u987e\u4e00\u4e0b\uff1a<\/p>\n
    \n
  1. \u60a8\u53ef\u4ee5\u5c06\u201c\u4f5c\u7528\u57df\u94fe\u201d\u89c6\u4e3a\u5bf9\u6211\u4eec\u53ef\u4ee5\u5728\u5f53\u524d\u4e0a\u4e0b\u6587\u4e2d\u8bbf\u95ee\u7684\u503c\u7684\u5f15\u7528\u94fe\u3002<\/li>\n
  2. \u4f5c\u7528\u57df\u8fd8\u4f7f\u5f97\u6211\u4eec\u53ef\u4ee5\u91cd\u7528\u5728\u4f5c\u7528\u57df\u94fe\u4e2d\u8f83\u4e0b\u65b9\u5b9a\u4e49\u7684\u53d8\u91cf\u540d\uff0c\u56e0\u4e3a\u4f5c\u7528\u57df\u94fe\u53ea\u80fd\u5411\u4e0b\u8bbf\u95ee\uff0c\u800c\u4e0d\u80fd\u5411\u4e0a\u3002<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"
    \u539f\u6587\u5730\u5740\uff1ahttps:\/\/dev.to\/lydiahallie\/javascript-visuali...<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2,20,3],"tags":[6,242],"class_list":["post-1795","post","type-post","status-publish","format-standard","hentry","category-all","category-frontend","category-tech","tag-javascript","tag-242"],"_links":{"self":[{"href":"https:\/\/zhuxinyong.com\/index.php?rest_route=\/wp\/v2\/posts\/1795","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/zhuxinyong.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/zhuxinyong.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/zhuxinyong.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/zhuxinyong.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1795"}],"version-history":[{"count":2,"href":"https:\/\/zhuxinyong.com\/index.php?rest_route=\/wp\/v2\/posts\/1795\/revisions"}],"predecessor-version":[{"id":1798,"href":"https:\/\/zhuxinyong.com\/index.php?rest_route=\/wp\/v2\/posts\/1795\/revisions\/1798"}],"wp:attachment":[{"href":"https:\/\/zhuxinyong.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1795"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/zhuxinyong.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1795"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/zhuxinyong.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1795"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}