In this lesson, we will learn about special characters that can clarify the character's positions in strings and substrings.
Let us look at the following example:
/java
/
java
Here, the word java
matches the string java
. It is a simple condition.
It is important to remember that regular expressions do not look for matches in strings but in substrings. If you search in a string containing characters besides the ones you look for, the check may show that the strings match, even though you did not want it:
/java
/
asdfjava
asdf
There are special characters to control character search in a string.
If you put ^
in the search line before the characters you look for, only the characters at the beginning of strings will match:
/^java
/
java
ruby clojurescript javascript
If we remove ^
, we will have two matches, including one in the last substring:
/java
/
java
ruby clojurescript java
script
This character is $
. Here is an example without this character. It has two matches:
/script
/
java ruby clojurescript
javascript
If we use $
, we will have only one match at the end of the string:
/script$
/
java ruby clojurescript javascript
Suppose we only need to find instances of a
at the end of a word. To do this, we type a\b
in the string pattern:
/a\b
/
java
ruby clojurescript javascript
If we type \B
, instead, we can invert the search and find all instances of a
not at the end of a word:
/a\B
/
ja
va ruby clojurescript ja
va
script
If you put \b
in front of the character we search for, we will find the characters at the beginning of the word:
/\bj
/
j
ava ruby clojurescript j
avascript
Here we use inverting again:
/\Bj
/
java ruby cloj
urescriptj
javascript
For clarity, if we compare it with the previous example, we added another j
after the clojurescript
in our string.
Now we find only instances of j
that are neither at the beginning nor the end of a word:
/\Bj\B
/
java ruby cloj
urescriptj javascript
The Hexlet support team or other students will answer you.
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