Javascript中奇怪的字符串拆分行为

Question

当我跑步时

'{{123}}'.split(/(\{\{)|(\}\})/g, -1)

我希望

["", "123", ""]

但它显示

["", "{{", undefined, "123", undefined, "}}", ""]

为什么？有什么不对吗？

Answer 1

使用：

'{{123}}'.split(/\{\{|\}\}/)

使用.split

时，您无需捕捉群组

Answer 2

http://es5.github.com/#x15.5.4.14

如果separator是包含捕获括号的正则表达式，则每次匹配时，捕获括号的结果（包括任何未定义的结果）都会拼接到输出数组中。例如，

"A<B>bold</B>and<CODE>coded</CODE>".split(/<(\/)?([^<>]+)>/)

计算数组

["A", undefined, "B", "bold", "/", "B", "and", undefined, "CODE", "coded", "/", "CODE", ""]

所以，'{{123}}'.split(/(\{\{)|(\}\})/g, -1)返回

["",
"{{", undefined, // "{{" is matched, but "}}" isn't.
"123",
undefined, "}}", // "{{" isn't matched, but "}}" is matched. 
""]