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<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>猎上网面试练习题</title>
</head>
  
<body>
<pre class="que">[] == ![];</pre>
<pre class="ans">
true
</pre>
<table class="step">
  <tr>
    <td></td>
    <td>[]</td>
    <td>==</td>
    <td>!Boolean([]);</td>
    <td>逻辑运算需进行数据类型转换</td>
  </tr>
  <tr>
    <td></td>
    <td>[]</td>
    <td>==</td>
    <td>!true</td>
    <td>0 NaN '' null undefined 在boolean中会变成false 其他为true</td>
  </tr>
  <tr>
    <td></td>
    <td>[]</td>
    <td>==</td>
    <td>false;</td>
    <td></td>
  </tr>
  <tr>
    <td></td>
    <td>[]</td>
    <td>==</td>
    <td>0;</td>
    <td>如果其中一项为bool值，另外一项不是，则将其转换成数字</td>
  </tr>
   <tr>
    <td></td>
    <td>toPrimitive([])</td>
    <td>==</td>
    <td>0;</td>
    <td>如果一项为对象，另一项为数字或字符串，则尝试将对象转换成primitiveValue原始值</td>
  </tr>
  <tr>
    <td></td>
    <td>[].valueOf()</td>
    <td>==</td>
    <td>0;</td>
    <td>首先尝试调用 valueOf  得到自身 仍然是对象类型</td>
  </tr>
  <tr>
    <td></td>
    <td>[]</td>
    <td>==</td>
    <td>0;</td>
    <td></td>
  </tr>
  <tr>
    <td></td>
    <td>[].toString()</td>
    <td>==</td>
    <td>0;</td>
    <td>再尝试调用  toString  </td>
  </tr>
  <tr>
    <td></td>
    <td>''</td>
    <td>==</td>
    <td>0;</td>
    <td>Array.toString返回一个字符串，使用逗号连接数组中所有元素</td>
  </tr>
  <tr>
    <td></td>
    <td>0</td>
    <td>==</td>
    <td>0</td>
    <td>字符串和数值进行比较时，将字符串转换成数值</td>
  </tr>
  <tr>
    <td></td>
    <td>0</td>
    <td>===</td>
    <td>0</td>
    <td>两边数据类型一致时，执行严格等运算</td>
  </tr>
   <tr>
    <td></td>
    <td></td>
    <td>true</td>
    <td></td>
    <td>得到结果true</td>
  </tr>
</table>
<pre class="que"><br/>var a = function( k ) { return false; };
a() && [] == ![];
</pre>
<pre class="ans">
false   
</pre>
<pre class="que"><br/>var k = true;
var a = function( k ){
    var k = k && true;
    return k;
};
a() && [] == ![];
</pre>
<pre class="ans">
undefined
</pre>
<pre class="que"><br/>var k = true;
var a = function( k ){
    var k = k && true;
    return k;
};
​
<label style="color:red">在这个区域输入什么代码，使其下列输出正常值</label>
​
a() && [] == ![]; 
​
</pre>
<pre class="ans">
a=function(){return k};
</pre>
<pre class="que"><br/>var arr = [ 1, 2 ];
arr.b = "123";
arr.toString();
​
</pre>
<pre class="ans">
'1,2'
</pre>
<pre class="que"><br/>var o = {
    a : 2,
    b : function(){
        this.a = 3;
        (function(){
            alert( this.a ); // 输出==>
            this.a = 4;
        })();
        alert( this.a );  // 输出==>
        return { d : o.a + 3 };
    }
};
o.b(); 
o.b.d; 
​
</pre>
<pre class="ans"><br/>
alert   undefined,
alert   3,
o.b.d   undefined
</pre>
<pre class="que"><br/>var i = 1, j = m = 0;
function a ( k ){
    return  k = k + 1;
}
​
j = a( i );
​
function a ( k ){
    return  k = k + 3;
}
​
m = a ( i );
j 
m 
​
​
</pre>
<pre class="ans"><br/>
j   4
m   4
</pre>
<pre class="que"><br/>alert( typeof a);
​
function a(){
    alert( "a.function" );
}
​
var a = "a.string";
​
alert( a );
​
</pre>
<pre class="ans"><br/>
alert function
alert a.string
</pre>
<pre class="que"><br/>var o = {
    a : function(){
        alert ( this.c ); 
    },
    c : " Hunteron "
};
​
( f = o.a )();
​
​
</pre>
<pre class="ans"><br/>
alert undefined
</pre>
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