{"id":3383,"date":"2024-11-10T16:51:21","date_gmt":"2024-11-10T08:51:21","guid":{"rendered":"https:\/\/fwq.ai\/blog\/3383\/"},"modified":"2024-11-10T16:51:21","modified_gmt":"2024-11-10T08:51:21","slug":"js%e5%a6%82%e4%bd%95%e6%af%94%e8%be%83%e6%9c%aa%e5%ae%9a%e4%b9%89%e7%9a%84%e5%80%bc","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/3383\/","title":{"rendered":"js\u5982\u4f55\u6bd4\u8f83\u672a\u5b9a\u4e49\u7684\u503c"},"content":{"rendered":"<blockquote><p>\n  \u5728 javascript \u4e2d\uff0c\u6bd4\u8f83\u672a\u5b9a\u4e49\u503c\u53ef\u4ee5\u901a\u8fc7\u4e25\u683c\u76f8\u7b49\u8fd0\u7b97\u7b26\uff08===\uff09\u6216\u5bbd\u677e\u76f8\u7b49\u8fd0\u7b97\u7b26\uff08==\uff09\u3002\u4e25\u683c\u76f8\u7b49\u8fd0\u7b97\u7b26\u68c0\u67e5\u503c\u548c\u7c7b\u578b\uff0c\u5bbd\u677e\u76f8\u7b49\u8fd0\u7b97\u7b26\u5c06\u503c\u8f6c\u6362\u4e3a\u76f8\u540c\u7c7b\u578b\u540e\u518d\u6bd4\u8f83\u3002\u672a\u5b9a\u4e49\u503c\u4e0e\u5176\u4ed6\u503c\u7684\u6bd4\u8f83\u9075\u5faa\u7279\u5b9a\u89c4\u5219\uff0c\u4f8b\u5982 undefined == null \u4e3a true\u3002\n<\/p><\/blockquote>\n<p><img decoding=\"async\" src=\"https:\/\/img.php.cn\/upload\/article\/202411\/08\/2024110811152411998.jpg\" class=\"aligncenter\" title=\"js\u5982\u4f55\u6bd4\u8f83\u672a\u5b9a\u4e49\u7684\u503c\u63d2\u56fe\" alt=\"js\u5982\u4f55\u6bd4\u8f83\u672a\u5b9a\u4e49\u7684\u503c\u63d2\u56fe\" \/><\/p>\n<p><strong>JavaScript \u4e2d\u6bd4\u8f83\u672a\u5b9a\u4e49\u503c<\/strong><\/p>\n<p>\u5728 JavaScript \u4e2d\uff0c\u6bd4\u8f83\u672a\u5b9a\u4e49\u503c\uff08undefined\uff09\u662f\u4e00\u4e2a\u5e38\u89c1\u7684\u64cd\u4f5c\u3002\u4ee5\u4e0b\u662f\u5982\u4f55\u505a\u5230\u8fd9\u4e00\u70b9\uff1a<\/p>\n<p><strong>\u4e25\u683c\u76f8\u7b49\u8fd0\u7b97\u7b26\uff08===\uff09<\/strong><\/p>\n<p>\u4e25\u683c\u76f8\u7b49\u8fd0\u7b97\u7b26\uff08===\uff09\u68c0\u67e5\u503c\u548c\u7c7b\u578b\u662f\u5426\u5b8c\u5168\u76f8\u7b49\u3002\u8981\u6bd4\u8f83\u672a\u5b9a\u4e49\u503c\uff0c\u4f7f\u7528\u4ee5\u4e0b\u8bed\u6cd5\uff1a<\/p>\n<pre>value === undefined<\/pre>\n<p>  \u767b\u5f55\u540e\u590d\u5236   <\/p>\n<p>\u5982\u679c value \u4e3a undefined\uff0c\u5219\u8be5\u8868\u8fbe\u5f0f\u7684\u503c\u4e3a true\uff1b\u5426\u5219\u4e3a false\u3002<\/p>\n<p><strong>\u5bbd\u677e\u76f8\u7b49\u8fd0\u7b97\u7b26\uff08==\uff09<\/strong><\/p>\n<p>\u5bbd\u677e\u76f8\u7b49\u8fd0\u7b97\u7b26\uff08==\uff09\u5c06\u503c\u8f6c\u6362\u4e3a\u76f8\u540c\u7c7b\u578b\u540e\u518d\u8fdb\u884c\u6bd4\u8f83\u3002\u8981\u6bd4\u8f83\u672a\u5b9a\u4e49\u503c\uff0c\u4f7f\u7528\u4ee5\u4e0b\u8bed\u6cd5\uff1a<\/p>\n<pre>value == undefined<\/pre>\n<p>  \u767b\u5f55\u540e\u590d\u5236   <\/p>\n<p>\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0cvalue \u5c06\u8f6c\u6362\u4e3a undefined\uff0c\u56e0\u6b64\u8be5\u8868\u8fbe\u5f0f\u7684\u503c\u4e3a true\u3002<\/p>\n<p><strong>\u6bd4\u8f83\u672a\u5b9a\u4e49\u503c\u4e0e\u5176\u4ed6\u503c<\/strong><\/p>\n<p>\u8981\u6bd4\u8f83\u672a\u5b9a\u4e49\u503c\u4e0e\u5176\u4ed6\u503c\uff0c\u8bf7\u4f7f\u7528\u4ee5\u4e0b\u89c4\u5219\uff1a<\/p>\n<ul>\n<li>undefined == null \u4e3a true\u3002<\/li>\n<li>undefined == false \u4e3a false\u3002<\/li>\n<li>undefined == 0 \u4e3a false\u3002<\/li>\n<li>undefined == &#8220;&#8221; \u4e3a false\u3002<\/li>\n<\/ul>\n<p><strong>\u793a\u4f8b<\/strong><\/p>\n<pre>console.log(undefined === undefined); \/\/ true\nconsole.log(undefined == null); \/\/ true\nconsole.log(undefined == false); \/\/ false\nconsole.log(undefined == 0); \/\/ false<\/pre>\n<p>  \u767b\u5f55\u540e\u590d\u5236   <\/p>\n<p>\u4ee5\u4e0a\u5c31\u662fjs\u5982\u4f55\u6bd4\u8f83\u672a\u5b9a\u4e49\u7684\u503c\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8\u7c73\u4e91\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5728 javascript \u4e2d\uff0c\u6bd4\u8f83\u672a\u5b9a\u4e49\u503c\u53ef\u4ee5\u901a\u8fc7\u4e25\u683c\u76f8\u7b49\u8fd0\u7b97\u7b26\uff08===\uff09\u6216\u5bbd\u677e\u76f8\u7b49\u8fd0\u7b97\u7b26\uff08==\uff09\u3002\u4e25\u683c\u76f8\u7b49\u8fd0\u7b97\u7b26\u68c0\u67e5\u503c\u548c\u7c7b\u578b\uff0c\u5bbd\u677e\u76f8\u7b49\u8fd0\u7b97\u7b26\u5c06\u503c\u8f6c\u6362\u4e3a\u76f8\u540c\u7c7b\u578b\u540e\u518d\u6bd4\u8f83\u3002\u672a\u5b9a\u4e49\u503c\u4e0e\u5176\u4ed6\u503c\u7684\u6bd4\u8f83\u9075\u5faa\u7279\u5b9a\u89c4\u5219\uff0c\u4f8b\u5982 undefined == null \u4e3a true\u3002 JavaScript \u4e2d\u6bd4\u8f83\u672a\u5b9a\u4e49\u503c \u5728 JavaScript \u4e2d\uff0c\u6bd4\u8f83\u672a\u5b9a\u4e49\u503c\uff08undefined\uff09\u662f\u4e00\u4e2a\u5e38\u89c1\u7684\u64cd\u4f5c\u3002\u4ee5\u4e0b\u662f\u5982\u4f55\u505a\u5230\u8fd9\u4e00\u70b9\uff1a \u4e25\u683c\u76f8\u7b49\u8fd0\u7b97\u7b26\uff08===\uff09 \u4e25\u683c\u76f8\u7b49\u8fd0\u7b97\u7b26\uff08===\uff09\u68c0\u67e5\u503c\u548c\u7c7b\u578b\u662f\u5426\u5b8c\u5168\u76f8\u7b49\u3002\u8981\u6bd4\u8f83\u672a\u5b9a\u4e49\u503c\uff0c\u4f7f\u7528\u4ee5\u4e0b\u8bed\u6cd5\uff1a value === undefined \u767b\u5f55\u540e\u590d\u5236 \u5982\u679c value \u4e3a undefined\uff0c\u5219\u8be5\u8868\u8fbe\u5f0f\u7684\u503c\u4e3a true\uff1b\u5426\u5219\u4e3a false\u3002 \u5bbd\u677e\u76f8\u7b49\u8fd0\u7b97\u7b26\uff08==\uff09 \u5bbd\u677e\u76f8\u7b49\u8fd0\u7b97\u7b26\uff08==\uff09\u5c06\u503c\u8f6c\u6362\u4e3a\u76f8\u540c\u7c7b\u578b\u540e\u518d\u8fdb\u884c\u6bd4\u8f83\u3002\u8981\u6bd4\u8f83\u672a\u5b9a\u4e49\u503c\uff0c\u4f7f\u7528\u4ee5\u4e0b\u8bed\u6cd5\uff1a value == undefined \u767b\u5f55\u540e\u590d\u5236 \u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0cvalue \u5c06\u8f6c\u6362\u4e3a undefined\uff0c\u56e0\u6b64\u8be5\u8868\u8fbe\u5f0f\u7684\u503c\u4e3a true\u3002 \u6bd4\u8f83\u672a\u5b9a\u4e49\u503c\u4e0e\u5176\u4ed6\u503c \u8981\u6bd4\u8f83\u672a\u5b9a\u4e49\u503c\u4e0e\u5176\u4ed6\u503c\uff0c\u8bf7\u4f7f\u7528\u4ee5\u4e0b\u89c4\u5219\uff1a undefined == null \u4e3a true\u3002 undefined == false \u4e3a false\u3002 undefined == 0 \u4e3a false\u3002 undefined == &#8220;&#8221; [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[],"class_list":["post-3383","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/3383","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/comments?post=3383"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/3383\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=3383"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=3383"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=3383"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}