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Repeat polyfill in Javascript
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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; | |
} | |
} |
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