{"id":68319,"date":"2019-06-25T14:12:10","date_gmt":"2019-06-25T06:12:10","guid":{"rendered":"http:\/\/www.xiaoyebailong.com\/?p=68319"},"modified":"2019-06-25T14:12:11","modified_gmt":"2019-06-25T06:12:11","slug":"if-else%e7%94%a8%e6%b3%95","status":"publish","type":"post","link":"http:\/\/www.xiaoyebailong.com\/index.php\/2019\/06\/25\/68319.htm","title":{"rendered":"if else\u7528\u6cd5"},"content":{"rendered":"\n<p>if \u548c else \u662f\u5199\u4ee3\u7801\u6700\u5e38\u7528\u7684\uff0c\u4f46\u662f\u5f80\u5f80\u540c\u5b66\u4eec\u4e0d\u4f1a\u53bb\u6df1\u5165\u7684\u4e86\u89e3\u4ed6\uff0c\u8fd9\u91cc\u6211\u5199\u51e0\u4e2aDemo\u73a9\u73a9\u3002<\/p>\n\n\n\n<p>\u9996\u5148\u7b80\u5355\u5217\u4e00\u4e0b\u4ec0\u4e48\u503c\u4f1a\u8fd4\u56detrue \uff0c \u4ec0\u4e48\u503c\u4f1a\u8fd4\u56defalse\u3002<\/p>\n\n\n\n<p>\u793a\u4f8b\uff1a<br>\n\u5f53\u53d8\u91cf a \u7684\u503c\u4e3a undefined&nbsp; unll&nbsp; 0&nbsp; false &#8220;&#8221;(\u7a7a\u5b57\u7b26\u4e32)&nbsp;\u65f6\uff0cif(a){}else{} \uff0c \u4f1a\u8fd4\u56defalse\uff0c\u8d70else\u3002<\/p>\n\n\n\n<p>\u5f53\u53d8\u91cf a \u7684\u503c\u4e3a\u6570\u503c\uff08\u6b63\u6570\u3001\u8d1f\u6570\uff09\uff0c\u5b57\u7b26\u4e32\uff08&#8217;null&#8217; or &#8216;undefined&#8217; or &#8216; &#8216; )\uff0ctrue \uff0cif(a){}else{} \uff0c \u4f1a\u8fd4\u56detrue\uff0c\u8d70 if \u3002<\/p>\n\n\n\n<p>demo1 (\u4e0d\u8981\u5728 if \u91cc\u9762\u76f4\u63a5\u5224\u65ad\u5c0f\u6570\u70b9\u4e4b\u95f4\u7684\u8fd0\u7b97\uff0c\u56e0\u4e3a js \u662f\u5f31\u7c7b\u578b\u8bed\u97f3\uff0c\u4e0d\u80fd\u8fdb\u884c\u5c0f\u6570\u70b9\u8fd0\u7b97,&nbsp;0.1 + 0.2 = 0.30000000000000004\uff0c0.1 * 0.2 = 0.20000000000000004)<\/p>\n\n\n\n<pre class=\"wp-block-syntaxhighlighter-code\">var a = 0.1+0.2\nif (a==0.3) {\n  console.log('log:\u6210\u7acb',)\n} else {\n  console.log('log:\u4e0d\u6210\u7acb')\n}\n\/\/log:\u4e0d\u6210\u7acb<\/pre>\n\n\n\n<p>demo2 (\u76f4\u63a5\u4f20\u4e00\u4e2a\u672a\u5b9a\u4e49\u7684\u53d8\u91cf\u5728 if \u91cc\u9762\u5224\u65ad\u4f1a\u5bfc\u81f4\u62a5\u9519\uff0c\u7ed3\u679c\u5c31\u662f if \u548c else \u90fd\u4e0d\u6267\u884c)<\/p>\n\n\n\n<pre class=\"wp-block-syntaxhighlighter-code\">if (b) {\n  console.log('log:1',)\n} else {\n  console.log('log:2')\n}\n\/\/ \u8fd0\u884c\u7ed3\u679c  \u62a5\u9519\uff0c\u6ca1\u6709log<\/pre>\n\n\n\n<p>demo3 ( 0 \u548c &#8220;&#8221; , js\u4e2d\u6570\u5b57 0 \u5c31\u662f false \uff0c&#8221;&#8221; \u7a7a\u5b57\u7b26\u4e32\u4e5f\u662ffalse)&nbsp;<\/p>\n\n\n\n<pre class=\"wp-block-syntaxhighlighter-code\">var c =0;\nvar d =\"\";\nif (c||d) {\n  console.log('log:\u8fd4\u56detrue')\n} else {\n  console.log('log:\u8fd4\u56defalse')\n}\n\/\/ \u8fd0\u884c\u7ed3\u679c  log:\u8fd4\u56defalse<\/pre>\n\n\n\n<p>demo4 (\u5b57\u7b26\u4e32&#8221;null&#8221; &#8220;undefined&#8221; &#8221; &#8221; \u90fd\u662f\u5c5e\u4e8e\u5b57\u7b26\u4e32\uff0c\u5e76\u4e14\u6709\u503c\uff0c\u6240\u4ee5\u4ed6\u4eec\u90fd\u662f\u8fd4\u56de true)<\/p>\n\n\n\n<pre class=\"wp-block-syntaxhighlighter-code\">var e = \"null\";\nvar f = \"undefined\";\nvar g = \" \";\nif (e || f || g) {\n  console.log('log:\u8fd4\u56detrue')\n} else {\n  console.log('log:\u8fd4\u56defalse')\n}<\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">    \/\/ \u8fd0\u884c\u7ed3\u679c  log:\u8fd4\u56detrue<\/h2>\n\n\n\n<p>\u4f5c\u8005\uff1aa_\u9756 <br>\n\u6765\u6e90\uff1aCSDN <br>\n\u539f\u6587\uff1ahttps:\/\/a-jing.blog.csdn.net\/article\/details\/93605508 <br>\n\u7248\u6743\u58f0\u660e\uff1a\u672c\u6587\u4e3a\u535a\u4e3b\u539f\u521b\u6587\u7ae0\uff0c\u8f6c\u8f7d\u8bf7\u9644\u4e0a\u535a\u6587\u94fe\u63a5\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>if \u548c else \u662f\u5199\u4ee3\u7801\u6700\u5e38\u7528\u7684\uff0c\u4f46\u662f\u5f80\u5f80\u540c\u5b66\u4eec\u4e0d\u4f1a\u53bb\u6df1\u5165\u7684\u4e86\u89e3\u4ed6\uff0c\u8fd9\u91cc\u6211\u5199\u51e0\u4e2aDemo\u73a9\u73a9\u3002 \u9996\u5148\u7b80\u5355\u5217\u4e00\u4e0b\u4ec0\u4e48\u503c\u4f1a\u8fd4\u56detrue \uff0c \u4ec0\u4e48\u503c\u4f1a\u8fd4\u56defalse\u3002 \u793a\u4f8b\uff1a \u5f53\u53d8\u91cf a \u7684\u503c\u4e3a undefined&nbsp; unll&#038;nb&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"topic":[],"class_list":["post-68319","post","type-post","status-publish","format-standard","hentry","category-wx"],"_links":{"self":[{"href":"http:\/\/www.xiaoyebailong.com\/index.php\/wp-json\/wp\/v2\/posts\/68319","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.xiaoyebailong.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.xiaoyebailong.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.xiaoyebailong.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.xiaoyebailong.com\/index.php\/wp-json\/wp\/v2\/comments?post=68319"}],"version-history":[{"count":1,"href":"http:\/\/www.xiaoyebailong.com\/index.php\/wp-json\/wp\/v2\/posts\/68319\/revisions"}],"predecessor-version":[{"id":68320,"href":"http:\/\/www.xiaoyebailong.com\/index.php\/wp-json\/wp\/v2\/posts\/68319\/revisions\/68320"}],"wp:attachment":[{"href":"http:\/\/www.xiaoyebailong.com\/index.php\/wp-json\/wp\/v2\/media?parent=68319"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.xiaoyebailong.com\/index.php\/wp-json\/wp\/v2\/categories?post=68319"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.xiaoyebailong.com\/index.php\/wp-json\/wp\/v2\/tags?post=68319"},{"taxonomy":"topic","embeddable":true,"href":"http:\/\/www.xiaoyebailong.com\/index.php\/wp-json\/wp\/v2\/topic?post=68319"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}