不带引号的JavaScript对象文字键的规则？ [英] Rules for unquoted JavaScript Object Literal Keys?

问题描述

在JavaScript中，您可以像这样定义一个对象：

  var d = {1：'test'}; 
  

我可以设置一个带负数索引的密钥，如下所示：

  d [-1] ='test2'; 
  

但如果我尝试在文字初始化中使用负数，我会收到错误：

  var d = {1：'test'， -  1：'test2'}; 
未捕获的SyntaxError：意外的令牌 -  
  

这是为什么？为什么我不能使用文字负数作为对象的键？是否有一种解决方法允许我将其初始化为文字。我知道我可以使用字符串，但我想使用整数。

解决方案

来自

In JavaScript, you can define an object like this:

var d = {1: 'test'};

and I can set a key with a negative number index like this:

d[-1] = 'test2';

but if I try to use a negative number in the literal initialization, I get an error:

var d = {1: 'test', -1: 'test2'};
Uncaught SyntaxError: Unexpected token -

Why is this? Why can't I use a literal negative number as a key to an object? Is there a workaround that allows me to initialize it as a literal. I know I could use strings instead, but I want to use integers.

解决方案

From Unquoted property names / object keys in JavaScript, my write-up on the subject:

Quotes can only be omitted if the property name is a numeric literal or a valid identifier name.

[…]

Bracket notation can safely be used for all property names.

[…]

Dot notation can only be used when the property name is a valid identifier name.

-1 is not a numeric literal, it’s a unary - operator followed by a numeric literal (1).

I also made a tool that will tell you if any given property name can be used without quotes and/or with dot notation. Try it at mothereff.in/js-properties.

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