test1 alert appears, test2 alert doesn't - invalid regex between them?

alert('test1');
var re = new RegExp("(http://(?:[A-Za-z0-9-]+\\.)?[A-Za-z0-9-]+\\.[A-Za-z0-9-]+/?)", "si");
alert('test2');

Why is this happening? How开发者_Go百科 to solve this problem?

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The "s" is the problem, it's not a valid modifier for javascript regular expressions. The only valid modifiers are /g (global) /i (case-insensitive) and /m (multi-line).