Revision 611365 of New in JavaScript 1.5

<p>JavaScript version 1.5 provides new features and enhancements described below.</p>

<h2 id="Runtime_errors">Runtime errors</h2>
<p>Runtime errors are now reported as exceptions.</p>

<h2 id="Number_formatting_enhancements">Number formatting enhancements</h2>
<p>Number formatting has been enhanced to include <code>Number.prototype.toExponential</code>, <code>Number.prototype.toFixed</code>, and <code>Number.prototype.toPrecision</code> methods. See the <a href="/en-US/docs/JavaScript/Guide/Obsolete_Pages/Predefined_Core_Objects/Number_Object" title="JavaScript/Guide/Obsolete_Pages/Predefined_Core_Objects/Number_Object">Number Object</a> page.</p>

<h2 id="Regular_expression_enhancements">Regular expression enhancements</h2>
<p>The following regular expression enhancements have been added:</p>
<ul>
  <li>Quantifiers — +, *, ? and {} — can now be followed by a ? to force them to be non-greedy. See the entry for ? on the <a href="/en-US/docs/JavaScript/Guide/Obsolete_Pages/Writing_a_Regular_Expression_Pattern#Using_Special_Characters" title="JavaScript/Guide/Obsolete_Pages/Writing_a_Regular_Expression_Pattern#Using_Special_Characters">Writing a Regular Expression Pattern</a> page.</li>
  <li>Non-capturing parentheses, (?:x) can be used instead of capturing parentheses, (x). When non-capturing parentheses are used, matched subexpressions are not available as back-references. See the entry for (?:x) on the <a href="/en-US/docs/JavaScript/Guide/Obsolete_Pages/Writing_a_Regular_Expression_Pattern#Using_Special_Characters" title="JavaScript/Guide/Obsolete_Pages/Writing_a_Regular_Expression_Pattern#Using_Special_Characters">Writing a Regular Expression Pattern</a> page.</li>
  <li>Positive and negative lookahead assertions are supported. Both assert a match depending on what follows the string being matched. See the entries for x(?=y) and x(?!y) on the <a href="/en-US/docs/JavaScript/Guide/Obsolete_Pages/Writing_a_Regular_Expression_Pattern#Using_Special_Characters" title="JavaScript/Guide/Obsolete_Pages/Writing_a_Regular_Expression_Pattern#Using_Special_Characters">Writing a Regular Expression Pattern</a> page.</li>
  <li>The m flag has been added to specify that the regular expression should match over multiple lines. See the <a href="/en-US/docs/JavaScript/Guide/Obsolete_Pages/Working_with_Regular_Expressions/Advanced_Searching_With_Flags" title="JavaScript/Guide/Obsolete_Pages/Working_with_Regular_Expressions/Advanced_Searching_With_Flags">Advanced Searching With Flags</a> page.</li>
</ul>

<h2 id="Conditional_function_declarations">Conditional function declarations</h2>
<p>Functions can now be declared inside an if clause. See the <a href="/en-US/docs/JavaScript/Guide/Obsolete_Pages/Defining_Functions" title="JavaScript/Guide/Obsolete_Pages/Defining_Functions">Defining Functions</a> page.</p>
<h2 id="Function_expressions">Function expressions</h2>
<p>Functions can now be declared inside an expression. See the <a href="/en-US/docs/JavaScript/Guide/Obsolete_Pages/Defining_Functions" title="JavaScript/Guide/Obsolete_Pages/Defining_Functions">Defining Functions</a> page.</p>

<h2 id="Multiple_catch_clauses">Multiple catch clauses</h2>
<p>Multiple catch clauses in a try...catch statement are supported. See <a href="/en-US/docs/JavaScript/Guide/Obsolete_Pages/Exception_Handling_Statements/try...catch_Statement#The_catch_Block" title="JavaScript/Guide/Obsolete_Pages/Exception_Handling_Statements/try...catch_Statement#The_catch_Block">The catch Block</a> page.</p>
<h2 id="Getters_and_setters">Getters and setters</h2>
<p>JavaScript writers can now add getters and setters to their objects. This feature is available only in the C implementation of JavaScript. See the <a href="/en-US/docs/JavaScript/Guide/Obsolete_Pages/Creating_New_Objects/Defining_Getters_and_Setters" title="JavaScript/Guide/Obsolete_Pages/Creating_New_Objects/Defining_Getters_and_Setters">Defining Getters and Setters</a> page.</p>

<h2 id="Constants">Constants</h2>
<p>Read-only named constants are supported. This feature is available only in the C implementation of JavaScript. See the <a href="/en-US/docs/JavaScript/Guide/Obsolete_Pages/Constants" title="JavaScript/Guide/Obsolete_Pages/Constants">Constants</a> page.</p>