Question

To use an operator like * or + on more than one element at a time, you can use parentheses. A part of a regular expression that is enclosed in parentheses counts as a single element as far as the operators following it are concerned.

var cartoonCrying = /boo+(hoo+)+/i;
console.log(cartoonCrying.test("Boohoooohoohooo"));
// → true

The first and second + characters apply only to the second o in boo and hoo, respectively. The third + applies to the whole group (hoo+) , matching one or more sequences like that.

The i at the end of the expression in the previous example makes this regular expression case insensitive, allowing it to match the uppercase B in the input string, even though the pattern is itself all lowercase.

This is a book about getting computers to do what you want them to do. Computers are about as common as screwdrivers today, but they contain a lot more hidden complexity and thus are harder to operate and understand. To many, they remain alien, slightly threatening things.