JavaScript property access: dot notation vs. brackets?答案

【问题标题】：JavaScript property access: dot notation vs. brackets?JavaScript property access: dot notation vs. brackets?
【发布时间】：2022-12-02 13:13:04
【问题描述】：

Other than the obvious fact that the first form could use a variable and not just a string literal, is there any reason to use one over the other, and if so under which cases?

In code:

// Given:
var foo = {\'bar\': \'baz\'};

// Then
var x = foo[\'bar\'];

// vs. 
var x = foo.bar;

Context: I\'ve written a code generator which produces these expressions and I\'m wondering which is preferable.

Just to chip in, not an answer to your original question (since you\'ve had plenty of good explanations so far), but speed-wise there\'s no difference worth mentioning either: jsperf.com/dot-vs-square-brackets. The above test gives only a 2% margin at best to either of them, they\'re neck and neck.
See also How do I add a property to an object using a variable as the name? and Dynamically access object property using variable
This question/answer can be used also for UTF-8 keys.

标签： javascript syntax object-literal

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