New in JavaScript 1.5

JavaScript 1.5版提供了如下的特性和功能曾强：

运行时错误(Runtime errors)
运行时错误(Runtime errors)将会被报告为异常(exceptions).

数字格式增强(Number formatting enhancements)
数字格式增加了Number.prototype.toExponential，Number.prototype.toFixed和Number.prototype.toPrecision方法。请参阅数字对象

正则表达式增强(Regular expression enhancements)
正则表达式添加了如下特性：

• Quantifiers — +, *, ? and {} — can now be followed by a ? to force them to be non-greedy. See the entry for ? on page Writing a Regular Expression Pattern.
• 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 page Writing a Regular Expression Pattern.
• 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 page Writing a Regular Expression Pattern.
• The m flag has been added to specify that the regular expression should match over multiple lines. See the Executing a Global Search, Ignoring Case, and Considering Multiline Input page.

Conditional function declarations
Functions can now be declared inside an if clause. See the Defining Functions page.

方法表达式(Function expressions)
方法(Functions)（对象）可以作为表达式的一部分。请参阅定义方法（对象）

多重catch子句(Multiple catch clauses)
在try...catch表达式中，可以定义多重catch子句。请参阅The catch Block

Getter和Setter(Getters and Setters)
JavsScript对对象(Object)提供了getter和setter方法。这个特性只存在于C语言实现的 JavaScript当中。请参阅定义Getter和Setter方法

常量(Constants)
Read only named constants are supported. This feature is available only in the C implementation of JavaScript. 请参阅常量