JavaScript 正则表达式“Nothing to repeat”错误
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JavaScript regular expression "Nothing to repeat" error
提问by Mustafa ELnagar
I have this error while trying to get the tokens the code to make the lexical analysis for the Minic langauge !
我在尝试获取标记代码以对 Minic 语言进行词法分析时遇到此错误！
document.writeln("1,2 3=()9,7".split(/,| |=|$|/));
document.writeln("<br>");
document.writeln("int sum ( int x , int y ) { int z = x + y ; }");
document.writeln("<br>");
document.writeln("int sum ( int x , int y ) { int z = x + y ; }".split(/,|*|-|+|=|<|>|!|&|,|/));
I get error on the debugger for the last line Uncaught SyntaxError: Invalid regular expression: Nothing to repeat !!
我在调试器的最后一行出现错误 Uncaught SyntaxError: Invalid regular expression: Nothing to repeat !!
回答by antyrat
回答by ThiefMaster
You need to escape the characters +and *since they have a special meaning in regexes. I also highly doubt that you wanted the last |- this adds the empty string to the matched elements and thus you get an array with one char per element.
您需要对字符进行转义+，*因为它们在正则表达式中具有特殊含义。我也非常怀疑您是否想要最后一个|- 这会将空字符串添加到匹配的元素中，因此您会得到一个每个元素一个字符的数组。
Here's the fixed regex:
这是固定的正则表达式：
/\*|-|\+|=|<|>|!|&|,/
However, you can make the it much more readable and maybe even faster by using a character class:
但是，您可以通过使用字符类使其更具可读性，甚至可能更快：
/[-,*+=<>!&]/
Demo:
演示：
js> "int sum ( int x , int y ) { int z = x + y ; }".split(/[-,*+=<>!&]/);
[ 'int sum ( int x ',
' int y ) { int z ',
' x ',
' y ; }' ]
