Converting User Input String to Regular Expression in JavaScript

In the design of a regular expression tester, the user's input string must be converted into a regular expression. However, if we specify that the user doesn't need to include //'s around the input, they won't be able to set flags like g and i.

To address this issue, we can utilize the RegExp object constructor to transform the user's input string into a regular expression. Here's how it works:

var re = new RegExp("a|b", "i");

This method achieves the same as:

var re = /a|b/i;

In the above examples, the first argument to the constructor is the regular expression pattern, and the second argument is the flags (optional). In this case, we specify the 'i' flag, which makes the pattern case-insensitive.

By using the RegExp object constructor, we can accept user input with //'s and flags while still ensuring the conversion to a regular expression. This allows users to utilize the full capabilities of regular expressions, including flag configuration, while maintaining user-friendliness.