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<!DOCTYPE html><html lang="en-GB-oxendict"><head><meta name="viewport" content="width=device-width, initial-scale=1"><meta charset="utf-8"><meta property="og:image" content="https://tc39.es/ecmarkup/ecma-logo.png"><meta property="og:title" content="ECMAScript® 2026 Language Specification"><meta property="og:description" content="Introduction
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This Ecma Standard defines the ECMAScript 2026 Language. It is the seventeenth edition of the ECMAScript Language Specification. ECMAScript is based on several originating technologies, the most well-known being JavaScript (Netscape) and JScript (Microsoft). The language was invent">
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<link rel="icon" href="../img/favicon.ico">
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<link rel="stylesheet" href="../assets/css/ecmarkup.css"><link rel="stylesheet" href="../assets/css/print.css" media="print">
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<title>ECMAScript® 2026 Language Specification</title><script src="../assets/js/multipage.js?cache=Wu2V1pj2" defer=""></script><script src="../assets/js/ecmarkup.js?cache=BPFBckdu" defer=""></script><link rel="canonical" href="../#sec-corrections-and-clarifications-in-ecmascript-2015-with-possible-compatibility-impact"></head>
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<body><div id="spec-container"><emu-annex id="sec-corrections-and-clarifications-in-ecmascript-2015-with-possible-compatibility-impact">
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<h1><span class="secnum">Annex E <span class="annex-kind">(informative)</span></span> Corrections and Clarifications in ECMAScript 2015 with Possible Compatibility Impact</h1>
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<p><emu-xref href="#sec-candeclareglobalvar" id="_ref_936"><a href="executable-code-and-execution-contexts.html#sec-candeclareglobalvar">9.1.1.4.14</a></emu-xref>-<emu-xref href="#sec-createglobalfunctionbinding" id="_ref_937"><a href="executable-code-and-execution-contexts.html#sec-createglobalfunctionbinding">9.1.1.4.17</a></emu-xref> Edition 5 and 5.1 used a property existence test to determine whether a <emu-xref href="#sec-global-object" id="_ref_17306"><a href="global-object.html#sec-global-object">global object</a></emu-xref> property corresponding to a new global declaration already existed. ECMAScript 2015 uses an own property existence test. This corresponds to what has been most commonly implemented by web browsers.</p>
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<p><emu-xref href="#sec-array-exotic-objects-defineownproperty-p-desc" id="_ref_938"><a href="ordinary-and-exotic-objects-behaviours.html#sec-array-exotic-objects-defineownproperty-p-desc">10.4.2.1</a></emu-xref>: The 5<sup>th</sup> Edition moved the capture of the current array length prior to the <emu-xref href="#integer" id="_ref_17307"><a href="notational-conventions.html#integer">integer</a></emu-xref> conversion of the <emu-xref href="#array-index" id="_ref_17308"><a href="ecmascript-data-types-and-values.html#array-index">array index</a></emu-xref> or new length value. However, the captured length value could become invalid if the conversion process has the side-effect of changing the array length. ECMAScript 2015 specifies that the current array length must be captured after the possible occurrence of such side-effects.</p>
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<p><emu-xref href="#sec-timeclip" id="_ref_939"><a href="numbers-and-dates.html#sec-timeclip">21.4.1.31</a></emu-xref>: Previous editions permitted the <emu-xref aoid="TimeClip" id="_ref_17309"><a href="numbers-and-dates.html#sec-timeclip">TimeClip</a></emu-xref> abstract operation to return either <emu-val>+0</emu-val><sub>𝔽</sub> or <emu-val>-0</emu-val><sub>𝔽</sub> as the representation of a 0 <emu-xref href="#sec-time-values-and-time-range" id="_ref_17310"><a href="numbers-and-dates.html#sec-time-values-and-time-range">time value</a></emu-xref>. ECMAScript 2015 specifies that <emu-val>+0</emu-val><sub>𝔽</sub> always returned. This means that for ECMAScript 2015 the <emu-xref href="#sec-time-values-and-time-range" id="_ref_17311"><a href="numbers-and-dates.html#sec-time-values-and-time-range">time value</a></emu-xref> of a Date is never observably <emu-val>-0</emu-val><sub>𝔽</sub> and methods that return <emu-xref href="#sec-time-values-and-time-range" id="_ref_17312"><a href="numbers-and-dates.html#sec-time-values-and-time-range">time values</a></emu-xref> never return <emu-val>-0</emu-val><sub>𝔽</sub>.</p>
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<p><emu-xref href="#sec-date-time-string-format" id="_ref_940"><a href="numbers-and-dates.html#sec-date-time-string-format">21.4.1.32</a></emu-xref>: If a UTC offset representation is not present, the local time zone is used. Edition 5.1 incorrectly stated that a missing time zone should be interpreted as <emu-val>"z"</emu-val>.</p>
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<p><emu-xref href="#sec-date.prototype.toisostring" id="_ref_941"><a href="numbers-and-dates.html#sec-date.prototype.toisostring">21.4.4.36</a></emu-xref>: If the year cannot be represented using the Date Time String Format specified in <emu-xref href="#sec-date-time-string-format" id="_ref_942"><a href="numbers-and-dates.html#sec-date-time-string-format">21.4.1.32</a></emu-xref> a RangeError exception is thrown. Previous editions did not specify the behaviour for that case.</p>
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<p><emu-xref href="#sec-date.prototype.tostring" id="_ref_943"><a href="numbers-and-dates.html#sec-date.prototype.tostring">21.4.4.41</a></emu-xref>: Previous editions did not specify the value returned by <code>Date.prototype.toString</code> when the <emu-xref href="#sec-time-values-and-time-range" id="_ref_17313"><a href="numbers-and-dates.html#sec-time-values-and-time-range">time value</a></emu-xref> is <emu-val>NaN</emu-val>. ECMAScript 2015 specifies the result to be the String value <emu-val>"Invalid Date"</emu-val>.</p>
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<p><emu-xref href="#sec-regexp-pattern-flags" id="_ref_944"><a href="text-processing.html#sec-regexp-pattern-flags">22.2.4.1</a></emu-xref>, <emu-xref href="#sec-escaperegexppattern" id="_ref_945"><a href="text-processing.html#sec-escaperegexppattern">22.2.6.13.1</a></emu-xref>: Any LineTerminator code points in the value of the <emu-val>"source"</emu-val> property of a RegExp instance must be expressed using an escape sequence. Edition 5.1 only required the escaping of <code>/</code>.</p>
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<p><emu-xref href="#sec-regexp.prototype-%symbol.match%" id="_ref_946"><a href="text-processing.html#sec-regexp.prototype-%symbol.match%">22.2.6.8</a></emu-xref>, <emu-xref href="#sec-regexp.prototype-%symbol.replace%" id="_ref_947"><a href="text-processing.html#sec-regexp.prototype-%symbol.replace%">22.2.6.11</a></emu-xref>: In previous editions, the specifications for <code>String.prototype.match</code> and <code>String.prototype.replace</code> was incorrect for cases where the pattern argument was a RegExp value whose <code>global</code> flag is set. The previous specifications stated that for each attempt to match the pattern, if <code>lastIndex</code> did not change, it should be incremented by 1. The correct behaviour is that <code>lastIndex</code> should be incremented by 1 only if the pattern matched the empty String.</p>
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<p><emu-xref href="#sec-array.prototype.sort" id="_ref_948"><a href="indexed-collections.html#sec-array.prototype.sort">23.1.3.30</a></emu-xref>: Previous editions did not specify how a <emu-val>NaN</emu-val> value returned by a <var>comparator</var> was interpreted by <code>Array.prototype.sort</code>. ECMAScript 2015 specifies that such as value is treated as if <emu-val>+0</emu-val><sub>𝔽</sub> was returned from the <var>comparator</var>. ECMAScript 2015 also specifies that <emu-xref aoid="ToNumber" id="_ref_17314"><a href="abstract-operations.html#sec-tonumber">ToNumber</a></emu-xref> is applied to the result returned by a <var>comparator</var>. In previous editions, the effect of a <var>comparator</var> result that <emu-xref href="#sec-ecmascript-language-types-number-type" id="_ref_17315"><a href="ecmascript-data-types-and-values.html#sec-ecmascript-language-types-number-type">is not a Number</a></emu-xref> value was <emu-xref href="#implementation-defined" id="_ref_17316"><a href="overview.html#implementation-defined">implementation-defined</a></emu-xref>. In practice, implementations call <emu-xref aoid="ToNumber" id="_ref_17317"><a href="abstract-operations.html#sec-tonumber">ToNumber</a></emu-xref>.</p>
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</emu-annex></div></body></html> |