Fri Nov 19 2021·2 min read
Photo by Alexander Popov
test() method to check if a regular expression matches an entire
/^hello$/.test(str). The caret
^ and dollar sign
$ match the
beginning and end of the string. The
test method returns
true if the regex
matches the entire string, and
const str = 'hello'; const test = /^hello$/.test(str); console.log(test); // 👉️ true const match = str.match(/^hello$/); console.log(match); // 👉️ ['hello']
We used the RegExp.test method to check if a regex matches an entire string.
The forward slashes
/ / mark the beginning and end of the regular expression.
^and dollar sign
$match the beginning and end of the input.
The caret lets us specify that the string has to start with a specific character and the dollar, that it has to end with the provided character. Anything in between also has to be matched.
If either of the conditions is not met, the
test method will return
const str = 'hello'; const test = /^hell$/.test(str); console.log(test); // 👉️ false
If you need to get an array containing the match(es), you can use the String.match method.
const str = 'hello123'; const match = str.match(/^hello[0-9]+$/); console.log(match); // 👉️ ['hello123']
Our regular expression uses a character class
 to check for a range of
0-9 at the end of the string.
+ matches one or more of the preceding item (digits).
match method returns an array containing the matches or
null if the
regular expression is not matched in the string.
You often have to handle the possible return value of
null, by using the
logical OR (||) operator.
const str = 'hello123'; const match = str.match(/^bye[0-9]+$/) || ; console.log(match); // 👉️ 
If there is no match, we return an empty array. This would prevent us from
getting an error when we try to access the array element at index
0 on a
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