JavaScript RegExp – (foo|bar|baz)

Regular expressions, also known as RegExp or regex, are a powerful tool in JavaScript that allow developers to search for patterns in strings. In JavaScript, we can use the RegExp object to create regular expressions. A regular expression consists of a pattern, which can include characters, groups, and quantifiers, among other things.

One pattern that we might want to search for is a particular set of words or phrases within a string. For example, let’s say we have a string that contains the words “foo”, “bar”, and “baz”, and we want to search for any of these words within the string. We can use the | character to create a logical OR operator within our pattern. Here’s an example:

const string = "The quick brown fox jumps over the lazy foo";
const regex = /foo|bar|baz/;
const match = regex.exec(string);

console.log(match[0]); // "foo"

In this example, we’re using the | character to create a pattern that matches any of the words “foo”, “bar”, or “baz”. We’re then using the exec() method on the RegExp object to find the first match within our string. This method returns an array where the first element is the matched text, in this case “foo”.

We can also use the test() method on the RegExp object to check if our pattern matches any part of a string, without returning the matched text. Here’s an example:

const string = "The quick brown fox jumps over the lazy bar";
const regex = /foo|bar|baz/;
const match = regex.test(string);

console.log(match); // true

In this example, we’re testing if our pattern matches any part of the string, but we’re not returning any matched text. The test() method returns a boolean value indicating whether there was a match.

It’s important to note that the | character has a lower precedence than other types of regular expression operators, such as grouping with parentheses (). This means that if we want our OR operator to apply to a group of characters, we need to enclose the group in parentheses. Here’s an example:

const string = "The quick brown fox jumps over the lazy foobar";
const regex = /(foo|bar|baz)+/;
const match = regex.exec(string);

console.log(match[0]); // "foobar"

In this example, we’re using parentheses to group the words “foo”, “bar”, and “baz” with the | operator. We’ve also added a + quantifier to the end of the group, which means that we expect one or more occurrences of the group. This time, the exec() method returns the entire matched string “foobar”, because it matches our group that includes the | operator.

In conclusion, using the | operator in a regular expression allows us to search for one or more specific words or phrases within a string. By combining the | operator with other regular expression operators, such as grouping with parentheses, we can create powerful patterns that can match any number of different text strings.