javascript lookahead

1Lookaheads are patterns that tell JavaScript to look-ahead in your string
2to check for patterns further along. This can be useful when you want to 
3search for multiple patterns over the same string.
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5A positive lookahead will look to make sure the element in the search
6pattern is there, but won't actually match it. A positive lookahead is used
7as (?=...) where the ... is the required part that is not matched.
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9On the other hand, a negative lookahead will look to make sure the element
10in the search pattern is not there. A negative lookahead is used as (?!...)
11where the ... is the pattern that you do not want to be there. The rest of 
12the pattern is returned if the negative lookahead part is not present.
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