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<h1 class="mume-header" id="%E7%BB%83%E4%B9%A0">练习</h1>
<h2 class="mume-header" id="%E5%AD%97%E7%AC%A6%E4%B8%B2%E5%92%8C%E5%8C%85%E8%A3%85%E5%AF%B9%E8%B1%A1">字符串和包装对象</h2>
<pre data-role="codeBlock" data-info="javascript" class="language-javascript"><span class="token keyword keyword-var">var</span> str <span class="token operator">=</span> <span class="token string">'abcd'</span>
str<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token string">'x'</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>str<span class="token punctuation">)</span>
<span class="token comment">/*
A. abcd
B. xbcd
C. 报错
D. x
*/</span>
</pre><pre data-role="codeBlock" data-info="javascript" class="language-javascript"><span class="token keyword keyword-var">var</span> s <span class="token operator">=</span> <span class="token string">'JQK'</span>
<span class="token keyword keyword-var">var</span> t <span class="token operator">=</span> <span class="token keyword keyword-new">new</span> <span class="token class-name">String</span><span class="token punctuation">(</span>s<span class="token punctuation">)</span>
t<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token string">'K'</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>t<span class="token punctuation">)</span>
<span class="token comment">/*
A. KQK
B. 报错
C. JQK
D. undefined
*/</span>
</pre><h2 class="mume-header" id="this%E6%8C%87%E5%90%91">this指向</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">'global'</span>
<span class="token keyword keyword-var">var</span> oa <span class="token operator">=</span> <span class="token punctuation">{</span>
name<span class="token operator">:</span> <span class="token string">'OA'</span><span class="token punctuation">,</span>
<span class="token function-variable function">myName</span><span class="token operator">:</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-return">return</span> <span class="token keyword keyword-this">this</span><span class="token punctuation">.</span><span class="token property-access">name</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token keyword keyword-var">var</span> ob <span class="token operator">=</span> <span class="token punctuation">{</span>
name<span class="token operator">:</span> <span class="token string">'OB'</span><span class="token punctuation">,</span>
<span class="token function-variable function">getName</span><span class="token operator">:</span> <span class="token keyword keyword-function">function</span> <span class="token punctuation">(</span><span class="token parameter">fun</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>fun <span class="token operator">&&</span> <span class="token keyword keyword-typeof">typeof</span> fun <span class="token operator">===</span> <span class="token string">'function'</span><span class="token punctuation">)</span>
<span class="token keyword control-flow keyword-return">return</span> <span class="token function">fun</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword control-flow keyword-return">return</span> <span class="token keyword keyword-this">this</span><span class="token punctuation">.</span><span class="token property-access">name</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> ob<span class="token punctuation">.</span><span class="token method function property-access">getName</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> ob<span class="token punctuation">.</span><span class="token method function property-access">getName</span><span class="token punctuation">(</span>oa<span class="token punctuation">.</span><span class="token property-access">myName</span><span class="token punctuation">)</span> <span class="token punctuation">)</span>
</pre><h2 class="mume-header" id="%E9%97%AD%E5%8C%85">闭包</h2>
<pre data-role="codeBlock" data-info="javascript" class="language-javascript"><span class="token keyword keyword-function">function</span> <span class="token function">fun</span><span class="token punctuation">(</span><span class="token parameter">n<span class="token punctuation">,</span>o</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>o<span class="token punctuation">)</span>
<span class="token keyword control-flow keyword-return">return</span> <span class="token punctuation">{</span>
<span class="token function-variable function">fun</span><span class="token operator">:</span><span class="token keyword keyword-function">function</span><span class="token punctuation">(</span><span class="token parameter">m</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
<span class="token keyword control-flow keyword-return">return</span> <span class="token function">fun</span><span class="token punctuation">(</span>m<span class="token punctuation">,</span>n<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 keyword keyword-var">var</span> a <span class="token operator">=</span> <span class="token function">fun</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span> a<span class="token punctuation">.</span><span class="token method function property-access">fun</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span> a<span class="token punctuation">.</span><span class="token method function property-access">fun</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 keyword keyword-var">var</span> b <span class="token operator">=</span> <span class="token function">fun</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 method function property-access">fun</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 method function property-access">fun</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 method function property-access">fun</span><span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword keyword-var">var</span> c <span class="token operator">=</span> <span class="token function">fun</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 method function property-access">fun</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span> c<span class="token punctuation">.</span><span class="token method function property-access">fun</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span> c<span class="token punctuation">.</span><span class="token method function property-access">fun</span><span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</pre>
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