In the previous chapter, we have already seen that in order to match a substring, you simply need to write the string inside a regular expression. For example, to match hello, you would create this variable:

var pattern = /hello/;

We also learned that if we want to match all occurrences of the string or character of the regular expression, we can use the g flag within Regex. However, situations where you have as clear a pattern like these are rare, and even when they come up, it's arguable whether Regex is even required. You really see the true power of regular expressions when you have less concrete information.

There are two main features the Regex engine implements that allow you to correctly represent 80 percent of your patterns. We will cover these two main features in this chapter: