Learning to Program

The Beginning and the End (of a Line)

Find and replace with regular expressions is pretty amazing, but one part of the previous regular expression is not quite right. The regular expression matches 'age=' and then some numbers. What if the author string also contained 'page=23'? Then our regular expression would match 'age=27' and 'page=23'. We could change our regular expression to be /(&age=)(\d+)/, but we would still have a problem: What if 'age' is at the beginning of the string and there is no preceding &? Fortunately, regular expressions have a way of identifying the beginning (and end) of a line. The beginning of a line is represented by a ^ (remember, the ^ has a different meaning inside brackets—regular expressions sure can be confusing), ...