代码拉取完成，页面将自动刷新
<!DOCTYPE html><html><head>
<title>js练习</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="file:///c:\Users\wy-ti\.vscode\extensions\shd101wyy.markdown-preview-enhanced-0.6.2\node_modules\@shd101wyy\mume\dependencies\katex\katex.min.css">
<style>
/**
* prism.js Github theme based on GitHub's theme.
* @author Sam Clarke
*/
code[class*="language-"],
pre[class*="language-"] {
color: #333;
background: none;
font-family: Consolas, "Liberation Mono", Menlo, Courier, monospace;
text-align: left;
white-space: pre;
word-spacing: normal;
word-break: normal;
word-wrap: normal;
line-height: 1.4;
-moz-tab-size: 8;
-o-tab-size: 8;
tab-size: 8;
-webkit-hyphens: none;
-moz-hyphens: none;
-ms-hyphens: none;
hyphens: none;
}
/* Code blocks */
pre[class*="language-"] {
padding: .8em;
overflow: auto;
/* border: 1px solid #ddd; */
border-radius: 3px;
/* background: #fff; */
background: #f5f5f5;
}
/* Inline code */
:not(pre) > code[class*="language-"] {
padding: .1em;
border-radius: .3em;
white-space: normal;
background: #f5f5f5;
}
.token.comment,
.token.blockquote {
color: #969896;
}
.token.cdata {
color: #183691;
}
.token.doctype,
.token.punctuation,
.token.variable,
.token.macro.property {
color: #333;
}
.token.operator,
.token.important,
.token.keyword,
.token.rule,
.token.builtin {
color: #a71d5d;
}
.token.string,
.token.url,
.token.regex,
.token.attr-value {
color: #183691;
}
.token.property,
.token.number,
.token.boolean,
.token.entity,
.token.atrule,
.token.constant,
.token.symbol,
.token.command,
.token.code {
color: #0086b3;
}
.token.tag,
.token.selector,
.token.prolog {
color: #63a35c;
}
.token.function,
.token.namespace,
.token.pseudo-element,
.token.class,
.token.class-name,
.token.pseudo-class,
.token.id,
.token.url-reference .token.variable,
.token.attr-name {
color: #795da3;
}
.token.entity {
cursor: help;
}
.token.title,
.token.title .token.punctuation {
font-weight: bold;
color: #1d3e81;
}
.token.list {
color: #ed6a43;
}
.token.inserted {
background-color: #eaffea;
color: #55a532;
}
.token.deleted {
background-color: #ffecec;
color: #bd2c00;
}
.token.bold {
font-weight: bold;
}
.token.italic {
font-style: italic;
}
/* JSON */
.language-json .token.property {
color: #183691;
}
.language-markup .token.tag .token.punctuation {
color: #333;
}
/* CSS */
code.language-css,
.language-css .token.function {
color: #0086b3;
}
/* YAML */
.language-yaml .token.atrule {
color: #63a35c;
}
code.language-yaml {
color: #183691;
}
/* Ruby */
.language-ruby .token.function {
color: #333;
}
/* Markdown */
.language-markdown .token.url {
color: #795da3;
}
/* Makefile */
.language-makefile .token.symbol {
color: #795da3;
}
.language-makefile .token.variable {
color: #183691;
}
.language-makefile .token.builtin {
color: #0086b3;
}
/* Bash */
.language-bash .token.keyword {
color: #0086b3;
}
/* highlight */
pre[data-line] {
position: relative;
padding: 1em 0 1em 3em;
}
pre[data-line] .line-highlight-wrapper {
position: absolute;
top: 0;
left: 0;
background-color: transparent;
display: block;
width: 100%;
}
pre[data-line] .line-highlight {
position: absolute;
left: 0;
right: 0;
padding: inherit 0;
margin-top: 1em;
background: hsla(24, 20%, 50%,.08);
background: linear-gradient(to right, hsla(24, 20%, 50%,.1) 70%, hsla(24, 20%, 50%,0));
pointer-events: none;
line-height: inherit;
white-space: pre;
}
pre[data-line] .line-highlight:before,
pre[data-line] .line-highlight[data-end]:after {
content: attr(data-start);
position: absolute;
top: .4em;
left: .6em;
min-width: 1em;
padding: 0 .5em;
background-color: hsla(24, 20%, 50%,.4);
color: hsl(24, 20%, 95%);
font: bold 65%/1.5 sans-serif;
text-align: center;
vertical-align: .3em;
border-radius: 999px;
text-shadow: none;
box-shadow: 0 1px white;
}
pre[data-line] .line-highlight[data-end]:after {
content: attr(data-end);
top: auto;
bottom: .4em;
}html body{font-family:"Helvetica Neue",Helvetica,"Segoe UI",Arial,freesans,sans-serif;font-size:16px;line-height:1.6;color:#333;background-color:#fff;overflow:initial;box-sizing:border-box;word-wrap:break-word}html body>:first-child{margin-top:0}html body h1,html body h2,html body h3,html body h4,html body h5,html body h6{line-height:1.2;margin-top:1em;margin-bottom:16px;color:#000}html body h1{font-size:2.25em;font-weight:300;padding-bottom:.3em}html body h2{font-size:1.75em;font-weight:400;padding-bottom:.3em}html body h3{font-size:1.5em;font-weight:500}html body h4{font-size:1.25em;font-weight:600}html body h5{font-size:1.1em;font-weight:600}html body h6{font-size:1em;font-weight:600}html body h1,html body h2,html body h3,html body h4,html body h5{font-weight:600}html body h5{font-size:1em}html body h6{color:#5c5c5c}html body strong{color:#000}html body del{color:#5c5c5c}html body a:not([href]){color:inherit;text-decoration:none}html body a{color:#08c;text-decoration:none}html body a:hover{color:#00a3f5;text-decoration:none}html body img{max-width:100%}html body>p{margin-top:0;margin-bottom:16px;word-wrap:break-word}html body>ul,html body>ol{margin-bottom:16px}html body ul,html body ol{padding-left:2em}html body ul.no-list,html body ol.no-list{padding:0;list-style-type:none}html body ul ul,html body ul ol,html body ol ol,html body ol ul{margin-top:0;margin-bottom:0}html body li{margin-bottom:0}html body li.task-list-item{list-style:none}html body li>p{margin-top:0;margin-bottom:0}html body .task-list-item-checkbox{margin:0 .2em .25em -1.8em;vertical-align:middle}html body .task-list-item-checkbox:hover{cursor:pointer}html body blockquote{margin:16px 0;font-size:inherit;padding:0 15px;color:#5c5c5c;background-color:#f0f0f0;border-left:4px solid #d6d6d6}html body blockquote>:first-child{margin-top:0}html body blockquote>:last-child{margin-bottom:0}html body hr{height:4px;margin:32px 0;background-color:#d6d6d6;border:0 none}html body table{margin:10px 0 15px 0;border-collapse:collapse;border-spacing:0;display:block;width:100%;overflow:auto;word-break:normal;word-break:keep-all}html body table th{font-weight:bold;color:#000}html body table td,html body table th{border:1px solid #d6d6d6;padding:6px 13px}html body dl{padding:0}html body dl dt{padding:0;margin-top:16px;font-size:1em;font-style:italic;font-weight:bold}html body dl dd{padding:0 16px;margin-bottom:16px}html body code{font-family:Menlo,Monaco,Consolas,'Courier New',monospace;font-size:.85em !important;color:#000;background-color:#f0f0f0;border-radius:3px;padding:.2em 0}html body code::before,html body code::after{letter-spacing:-0.2em;content:"\00a0"}html body pre>code{padding:0;margin:0;font-size:.85em !important;word-break:normal;white-space:pre;background:transparent;border:0}html body .highlight{margin-bottom:16px}html body .highlight pre,html body pre{padding:1em;overflow:auto;font-size:.85em !important;line-height:1.45;border:#d6d6d6;border-radius:3px}html body .highlight pre{margin-bottom:0;word-break:normal}html body pre code,html body pre tt{display:inline;max-width:initial;padding:0;margin:0;overflow:initial;line-height:inherit;word-wrap:normal;background-color:transparent;border:0}html body pre code:before,html body pre tt:before,html body pre code:after,html body pre tt:after{content:normal}html body p,html body blockquote,html body ul,html body ol,html body dl,html body pre{margin-top:0;margin-bottom:16px}html body kbd{color:#000;border:1px solid #d6d6d6;border-bottom:2px solid #c7c7c7;padding:2px 4px;background-color:#f0f0f0;border-radius:3px}@media print{html body{background-color:#fff}html body h1,html body h2,html body h3,html body h4,html body h5,html body h6{color:#000;page-break-after:avoid}html body blockquote{color:#5c5c5c}html body pre{page-break-inside:avoid}html body table{display:table}html body img{display:block;max-width:100%;max-height:100%}html body pre,html body code{word-wrap:break-word;white-space:pre}}.markdown-preview{width:100%;height:100%;box-sizing:border-box}.markdown-preview .pagebreak,.markdown-preview .newpage{page-break-before:always}.markdown-preview pre.line-numbers{position:relative;padding-left:3.8em;counter-reset:linenumber}.markdown-preview pre.line-numbers>code{position:relative}.markdown-preview pre.line-numbers .line-numbers-rows{position:absolute;pointer-events:none;top:1em;font-size:100%;left:0;width:3em;letter-spacing:-1px;border-right:1px solid #999;-webkit-user-select:none;-moz-user-select:none;-ms-user-select:none;user-select:none}.markdown-preview pre.line-numbers .line-numbers-rows>span{pointer-events:none;display:block;counter-increment:linenumber}.markdown-preview pre.line-numbers .line-numbers-rows>span:before{content:counter(linenumber);color:#999;display:block;padding-right:.8em;text-align:right}.markdown-preview .mathjax-exps .MathJax_Display{text-align:center !important}.markdown-preview:not([for="preview"]) .code-chunk .btn-group{display:none}.markdown-preview:not([for="preview"]) .code-chunk .status{display:none}.markdown-preview:not([for="preview"]) .code-chunk .output-div{margin-bottom:16px}.scrollbar-style::-webkit-scrollbar{width:8px}.scrollbar-style::-webkit-scrollbar-track{border-radius:10px;background-color:transparent}.scrollbar-style::-webkit-scrollbar-thumb{border-radius:5px;background-color:rgba(150,150,150,0.66);border:4px solid rgba(150,150,150,0.66);background-clip:content-box}html body[for="html-export"]:not([data-presentation-mode]){position:relative;width:100%;height:100%;top:0;left:0;margin:0;padding:0;overflow:auto}html body[for="html-export"]:not([data-presentation-mode]) .markdown-preview{position:relative;top:0}@media screen and (min-width:914px){html body[for="html-export"]:not([data-presentation-mode]) .markdown-preview{padding:2em calc(50% - 457px + 2em)}}@media screen and (max-width:914px){html body[for="html-export"]:not([data-presentation-mode]) .markdown-preview{padding:2em}}@media screen and (max-width:450px){html body[for="html-export"]:not([data-presentation-mode]) .markdown-preview{font-size:14px !important;padding:1em}}@media print{html body[for="html-export"]:not([data-presentation-mode]) #sidebar-toc-btn{display:none}}html body[for="html-export"]:not([data-presentation-mode]) #sidebar-toc-btn{position:fixed;bottom:8px;left:8px;font-size:28px;cursor:pointer;color:inherit;z-index:99;width:32px;text-align:center;opacity:.4}html body[for="html-export"]:not([data-presentation-mode])[html-show-sidebar-toc] #sidebar-toc-btn{opacity:1}html body[for="html-export"]:not([data-presentation-mode])[html-show-sidebar-toc] .md-sidebar-toc{position:fixed;top:0;left:0;width:300px;height:100%;padding:32px 0 48px 0;font-size:14px;box-shadow:0 0 4px rgba(150,150,150,0.33);box-sizing:border-box;overflow:auto;background-color:inherit}html body[for="html-export"]:not([data-presentation-mode])[html-show-sidebar-toc] .md-sidebar-toc::-webkit-scrollbar{width:8px}html body[for="html-export"]:not([data-presentation-mode])[html-show-sidebar-toc] .md-sidebar-toc::-webkit-scrollbar-track{border-radius:10px;background-color:transparent}html body[for="html-export"]:not([data-presentation-mode])[html-show-sidebar-toc] .md-sidebar-toc::-webkit-scrollbar-thumb{border-radius:5px;background-color:rgba(150,150,150,0.66);border:4px solid rgba(150,150,150,0.66);background-clip:content-box}html body[for="html-export"]:not([data-presentation-mode])[html-show-sidebar-toc] .md-sidebar-toc a{text-decoration:none}html body[for="html-export"]:not([data-presentation-mode])[html-show-sidebar-toc] .md-sidebar-toc ul{padding:0 1.6em;margin-top:.8em}html body[for="html-export"]:not([data-presentation-mode])[html-show-sidebar-toc] .md-sidebar-toc li{margin-bottom:.8em}html body[for="html-export"]:not([data-presentation-mode])[html-show-sidebar-toc] .md-sidebar-toc ul{list-style-type:none}html body[for="html-export"]:not([data-presentation-mode])[html-show-sidebar-toc] .markdown-preview{left:300px;width:calc(100% - 300px);padding:2em calc(50% - 457px - 150px);margin:0;box-sizing:border-box}@media screen and (max-width:1274px){html body[for="html-export"]:not([data-presentation-mode])[html-show-sidebar-toc] .markdown-preview{padding:2em}}@media screen and (max-width:450px){html body[for="html-export"]:not([data-presentation-mode])[html-show-sidebar-toc] .markdown-preview{width:100%}}html body[for="html-export"]:not([data-presentation-mode]):not([html-show-sidebar-toc]) .markdown-preview{left:50%;transform:translateX(-50%)}html body[for="html-export"]:not([data-presentation-mode]):not([html-show-sidebar-toc]) .md-sidebar-toc{display:none}
/* Please visit the URL below for more information: */
/* https://shd101wyy.github.io/markdown-preview-enhanced/#/customize-css */
</style>
</head>
<body for="html-export">
<div class="mume markdown-preview ">
<h2 class="mume-header" id="%E5%8F%98%E9%87%8F%E6%8F%90%E5%8D%87">变量提升</h2>
<pre data-role="codeBlock" data-info="javascript" class="language-javascript"><span class="token keyword keyword-var">var</span> name <span class="token operator">=</span> <span class="token string">'World!'</span><span class="token punctuation">;</span>
<span class="token punctuation">(</span><span class="token keyword keyword-function">function</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword control-flow keyword-if">if</span> <span class="token punctuation">(</span><span class="token keyword keyword-typeof">typeof</span> name <span class="token operator">===</span> <span class="token string">'undefined'</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword keyword-var">var</span> name <span class="token operator">=</span> <span class="token string">'Jack'</span><span class="token punctuation">;</span>
<span class="token console class-name">console</span><span class="token punctuation">.</span><span class="token method function property-access">log</span><span class="token punctuation">(</span><span class="token string">'Goodbye '</span> <span class="token operator">+</span> name<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span> <span class="token keyword control-flow keyword-else">else</span> <span class="token punctuation">{</span>
<span class="token console class-name">console</span><span class="token punctuation">.</span><span class="token method function property-access">log</span><span class="token punctuation">(</span><span class="token string">'Hello '</span> <span class="token operator">+</span> name<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// A. Goodbye Jack</span>
<span class="token comment">// B. Hello Jack</span>
<span class="token comment">// C. Hello undefined</span>
<span class="token comment">// D. Hello World</span>
</pre><h2 class="mume-header" id="%E7%B1%BB%E5%9E%8B%E8%BD%AC%E6%8D%A2">类型转换</h2>
<pre data-role="codeBlock" data-info="javascript" class="language-javascript"><span class="token keyword keyword-var">var</span> a <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword control-flow keyword-if">if</span> <span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token console class-name">console</span><span class="token punctuation">.</span><span class="token method function property-access">log</span><span class="token punctuation">(</span>a <span class="token operator">==</span> <span class="token boolean">true</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span> <span class="token keyword control-flow keyword-else">else</span> <span class="token punctuation">{</span>
<span class="token console class-name">console</span><span class="token punctuation">.</span><span class="token method function property-access">log</span><span class="token punctuation">(</span><span class="token string">"wut"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token comment">// A. true</span>
<span class="token comment">// B. false</span>
<span class="token comment">// C. "wut"</span>
<span class="token comment">// D. other</span>
</pre><h2 class="mume-header" id>==</h2>
<pre data-role="codeBlock" data-info="javascript" class="language-javascript"><span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token operator">==</span><span class="token punctuation">[</span><span class="token punctuation">]</span>
<span class="token comment">// A. true</span>
<span class="token comment">// B. false</span>
<span class="token comment">// C. error</span>
<span class="token comment">// D. other</span>
</pre><pre data-role="codeBlock" data-info="javascript" class="language-javascript"><span class="token number">2</span> <span class="token operator">==</span> <span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">]</span>
<span class="token comment">// A. true</span>
<span class="token comment">// B. false</span>
<span class="token comment">// C. undefined</span>
<span class="token comment">// D. other</span>
</pre><h2 class="mume-header" id="%E6%8F%90%E5%8D%87%E5%85%A8%E5%B1%80%E5%8F%98%E9%87%8F">提升全局变量</h2>
<pre data-role="codeBlock" data-info="javascript" class="language-javascript"><span class="token punctuation">(</span><span class="token keyword keyword-function">function</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword keyword-var">var</span> x <span class="token operator">=</span> y <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token console class-name">console</span><span class="token punctuation">.</span><span class="token method function property-access">log</span><span class="token punctuation">(</span>y<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token console class-name">console</span><span class="token punctuation">.</span><span class="token method function property-access">log</span><span class="token punctuation">(</span>x<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// A. 1, 1</span>
<span class="token comment">// B. error, error</span>
<span class="token comment">// C. 1, error</span>
<span class="token comment">// D. other</span>
</pre><h2 class="mume-header" id="arguments">arguments</h2>
<pre data-role="codeBlock" data-info="javascript" class="language-javascript"><span class="token keyword keyword-function">function</span> <span class="token function">sidEffecting</span><span class="token punctuation">(</span><span class="token parameter">ary</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
ary<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> ary<span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword keyword-function">function</span> <span class="token function">bar</span><span class="token punctuation">(</span><span class="token parameter">a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> c</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
c <span class="token operator">=</span> <span class="token number">10</span><span class="token punctuation">;</span>
<span class="token function">sidEffecting</span><span class="token punctuation">(</span>arguments<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword control-flow keyword-return">return</span> a <span class="token operator">+</span> b <span class="token operator">+</span> c<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token function">bar</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// A. 3</span>
<span class="token comment">// B. 12</span>
<span class="token comment">// C. error</span>
<span class="token comment">// D. 21</span>
</pre>
</div>
</body></html>
此处可能存在不合适展示的内容，页面不予展示。您可通过相关编辑功能自查并修改。
如您确认内容无涉及 不当用语 / 纯广告导流 / 暴力 / 低俗色情 / 侵权 / 盗版 / 虚假 / 无价值内容或违法国家有关法律法规的内容，可点击提交进行申诉，我们将尽快为您处理。
马建仓 AI 助手
