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
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
|
---
title: String.prototype.repeat()
slug: Web/JavaScript/Reference/Global_Objects/String/repeat
translation_of: Web/JavaScript/Reference/Global_Objects/String/repeat
original_slug: Web/JavaScript/Referencje/Obiekty/String/repeat
---
<div>{{JSRef}}</div>
<p>The <strong><code>repeat()</code></strong> method constructs and returns a new string which contains the specified number of copies of the string on which it was called, concatenated together.</p>
<h2 id="Składnia">Składnia</h2>
<pre class="syntaxbox"><var>str</var>.repeat(<var>count</var>)</pre>
<h3 id="Parametry">Parametry</h3>
<dl>
<dt><code>count</code></dt>
<dd>An integer between 0 and +∞: [0, +∞), indicating the number of times to repeat the string in the newly-created string that is to be returned.</dd>
</dl>
<h3 id="Zwracana_wartość">Zwracana wartość</h3>
<p>A new string containing the specified number of copies of the given string.</p>
<h3 id="Exceptions">Exceptions</h3>
<ul>
<li>{{jsxref("Errors/Negative_repetition_count", "RangeError")}}: repeat count must be non-negative.</li>
<li>{{jsxref("Errors/Resulting_string_too_large", "RangeError")}}: repeat count must be less than infinity and not overflow maximum string size.</li>
</ul>
<h2 id="Przykłady">Przykłady</h2>
<pre class="brush: js">'abc'.repeat(-1); // RangeError
'abc'.repeat(0); // ''
'abc'.repeat(1); // 'abc'
'abc'.repeat(2); // 'abcabc'
'abc'.repeat(3.5); // 'abcabcabc' (count will be converted to integer)
'abc'.repeat(1/0); // RangeError
({ toString: () => 'abc', repeat: String.prototype.repeat }).repeat(2);
// 'abcabc' (repeat() is a generic method)
</pre>
<h2 id="Polyfill">Polyfill</h2>
<p>This method has been added to the ECMAScript 6 specification and may not be available in all JavaScript implementations yet. However, you can polyfill <code>String.prototype.repeat()</code> with the following snippet:</p>
<pre class="brush: js">if (!String.prototype.repeat) {
String.prototype.repeat = function(count) {
'use strict';
if (this == null) {
throw new TypeError('can\'t convert ' + this + ' to object');
}
var str = '' + this;
count = +count;
if (count != count) {
count = 0;
}
if (count < 0) {
throw new RangeError('repeat count must be non-negative');
}
if (count == Infinity) {
throw new RangeError('repeat count must be less than infinity');
}
count = Math.floor(count);
if (str.length == 0 || count == 0) {
return '';
}
// Ensuring count is a 31-bit integer allows us to heavily optimize the
// main part. But anyway, most current (August 2014) browsers can't handle
// strings 1 << 28 chars or longer, so:
if (str.length * count >= 1 << 28) {
throw new RangeError('repeat count must not overflow maximum string size');
}
var rpt = '';
for (;;) {
if ((count & 1) == 1) {
rpt += str;
}
count >>>= 1;
if (count == 0) {
break;
}
str += str;
}
// Could we try:
// return Array(count + 1).join(this);
return rpt;
}
}
</pre>
<h2 id="Specifications">Specifications</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-string.prototype.repeat', 'String.prototype.repeat')}}</td>
<td>{{Spec2('ES6')}}</td>
<td>Initial definition.</td>
</tr>
<tr>
<td>{{SpecName('ESDraft', '#sec-string.prototype.repeat', 'String.prototype.repeat')}}</td>
<td>{{Spec2('ESDraft')}}</td>
<td> </td>
</tr>
</tbody>
</table>
<h2 id="Browser_compatibility">Browser compatibility</h2>
<div>{{CompatibilityTable}}</div>
<div id="compat-desktop">
<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>{{CompatChrome("41")}} </td>
<td>{{CompatGeckoDesktop("24")}}</td>
<td>{{CompatNo}}</td>
<td>{{CompatNo}}</td>
<td>{{CompatSafari("9")}}</td>
</tr>
</tbody>
</table>
</div>
<div id="compat-mobile">
<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>{{CompatChrome("36")}}</td>
<td>{{CompatGeckoMobile("24")}}</td>
<td>{{CompatNo}}</td>
<td>{{CompatNo}}</td>
<td>{{CompatNo}}</td>
</tr>
</tbody>
</table>
</div>
|
