blob: 0174ccd5bcc3f7b3131c24d8a99cb8d33f5366e9 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
|
---
title: Set.prototype.has()
slug: Web/JavaScript/Reference/Global_Objects/Set/has
tags:
- ECMAScript 2015
- JavaScript
- set
translation_of: Web/JavaScript/Reference/Global_Objects/Set/has
---
<div>{{JSRef("Global_Objects", "Set")}}</div>
<h2 id="Summary">概述</h2>
<p><strong>has() </strong>方法返回一个布尔值来指示对应的值value是否存在Set对象中。</p>
<h2 id="Syntax">语法</h2>
<pre class="syntaxbox"><code><em>mySet</em>.has(value);</code></pre>
<h3 id="参数">参数</h3>
<dl>
<dt>value</dt>
<dd>必需。用以测试该值是否存在于 Set 对象中。</dd>
</dl>
<h3 id="返回值">返回值</h3>
<dl>
<dt>Boolean</dt>
<dd>如果指定的值（value）存在于Set对象当中，返回<code>true</code>；否则返回 <code>false</code>。</dd>
</dl>
<h2 id="Examples">示例</h2>
<h3 id="Example:_Testing_size_of_all_array_elements">使用 <code>has</code> 方法</h3>
<pre class="brush: js line-numbers language-js">var mySet = new Set();
mySet.add('foo');
mySet.has('foo'); // 返回 true
mySet.has('bar'); // 返回 false
var set1 = new Set();
var obj1 = {'key1': 1};
set1.add(obj1);
set1.has(obj1); // 返回 true
set1.has({'key1': 1}); // 会返回 false，因为其是另一个对象的引用
set1.add({'key1': 1}); // 现在 set1 中有2条（不同引用的）对象了</pre>
<h2 id="规范">规范</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">Specification</th>
<th scope="col">Status</th>
<th scope="col">Comment</th>
</tr>
<tr>
<td>{{SpecName('ES6', '#sec-set.prototype.has', 'Set.prototype.has')}}</td>
<td>{{Spec2('ES6')}}</td>
<td>Initial definition.</td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<p>{{ CompatibilityTable() }}</p>
<div>
<table class="compat-table">
<tbody>
<tr>
<th>Feature</th>
<th>Chrome</th>
<th>Firefox (Gecko)</th>
<th>Internet Explorer</th>
<th>Opera</th>
<th>Safari</th>
</tr>
<tr>
<td>Basic support</td>
<td>38</td>
<td>{{CompatGeckoDesktop("13.0")}}</td>
<td>11</td>
<td>25</td>
<td>7.1</td>
</tr>
</tbody>
</table>
</div>
<div>
<table class="compat-table">
<tbody>
<tr>
<th>Feature</th>
<th>Android</th>
<th>Chrome for Android</th>
<th>Firefox Mobile (Gecko)</th>
<th>IE Mobile</th>
<th>Opera Mobile</th>
<th>Safari Mobile</th>
</tr>
<tr>
<td>Basic support</td>
<td>{{ CompatNo() }}</td>
<td>38</td>
<td>{{CompatGeckoMobile("13.0")}}</td>
<td>{{ CompatNo() }}</td>
<td>{{ CompatNo() }}</td>
<td>iOS 8</td>
</tr>
</tbody>
</table>
</div>
<h2 id="相关连接"><strong>相关连接</strong></h2>
<ul>
<li>{{jsxref("Set")}}</li>
<li>{{jsxref("Set.prototype.add()")}}</li>
<li>{{jsxref("Set.prototype.delete()")}}</li>
</ul>
|
