JS - RegExp for detecting ".-" , "-."

I am bit confused with the RegExp I should be using to detect ".-", "-." it indeed passes this combinations as valid but in the same time, "-_","_-" get validated as well. Am I missing something or not escaping something properly?

 var reg=new RegExp("(\.\-)|(\-\.)");开发者_如何学编程

Actually seems any combination containing '-' gets passed. it

Got it thank you everyone.

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You need to use

"(\\.-)|(-\\.)"

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Since you're using a string with the RegExp constructor rather than /, you need to escape twice.

>>> "asd_-ads".search("(\.\-)|(\-\.)")
3
>>> "asd_-ads".search(/(\.\-)|(\-\.)/)
-1
>>> "asd_-ads".search(new RegExp('(\\.\-)|(\-\\.)'))
-1

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In notation /(\.\-)|(\-\.)/, the expression would be right. In the notation you chose, you must double all backslashes, because it still has a special meaning of itself, like \\, \n and so on.
Note there is no need to escape the dash here: var reg = new RegExp("(\\.-)|(-\\.)");

If you don't need to differentiate the matches, you can use a single enclosing capture, or none at all if you only want to check the match: "\\.-|-\\." is still valid.

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You are using double quotes so the . doesn't get escaped with one backslash, use this notation:

var reg = /(\.\-)|(\-\.)/;