.length — Finding the length of the string
This one may seem obvious, but it is likely the most important string method and undoubtedly the most commonly used one. Calling
.length on a string will return the number of character that the string contains.
.trim() — Removing white space
trim() function removes white space from the beginning and end of a string. You will find yourself using this one most often when processing the string of a user input field. It is easy to accidentally add spaces, and this ensures you handle the relevant characters.
.includes() — Determine if string contains substring
includes() function determines if a substring is contained in a larger string and returns
false. This has many applications, but one common use-case is for string matching for searching/parsing.
.indexOf() — Finding the index of a substring
indexOf() was the primary way you would check if a substring existed in a string. It is likely you will still see code that uses
indexOf, so understanding how it works is important. The function returns the index of the substring within the string. If the substring is not contained in the original string, it will return
The common pattern for
indexOf() which mimics the behavior of
includes() which is to check if the index is greater than -1:
.toUpperCase() — Capitalizes entire string
toUpperCase() function returns a string with all upper case letters.
.toLowerCase() — Lower cases entire string
toLowerCase() function returns a string with all lower case letters.
.replace() — Replaces strings with new values
replace() function is called on a string and will return a string with a
pattern replaced by a
replacement string. It takes either a regex or a string as the
pattern. With a regex you can globally replace all matches (using the
g option), but with a string it will only replace the first occurrence. In the example below, you will notice that
world is replaced only once in the first call since it uses a string pattern.
.slice() — Return a section of a string
slice() method will extract a section of a string based on the index supplied and return it as a new string. This is useful when you know the structure of a string and want to retrieve a certain portion, or it can be used with the
indexOf method which we learned earlier where you can find the index of the first occurrence of a substring and use that as a reference point for slicing.
slice() takes the beginning index as the first parameter and an optional ending index as the second parameter —
str.slice(beginIndex[, endIndex]). If no ending index is supplied, it slices to the end of the string starting with your
beginIndex. If a negative
beginIndex is used, it will slice backwards from the end of the string. The following is an example from MDN which depicts these cases.
.split() — Converts string into an array of strings
split() method takes a
separator which you want to split apart the string on, and it returns an array of strings. This is useful when you know your string uses a certain character to separate data, or if you want to operate on specific substrings individually.
.repeat() — Repeats a string a specified number of times
repeat() function returns a string consisting of the elements of the object repeated the given number of times.
.match() — Returns array of matching strings
match() method retrieves the matches when matching a
string against a
regular expression. The example below searches our string for all capital letters. It returns an array of strings for the values that match the regex.
.charAt() — Returns the character at an index
charAt() function returns the string character at a given index.
.charCodeAt() —Return the unicode at an index
charCodeAt() method returns the unicode of the character at a specified index in a string. This an UTF-16 cone integer between 0 and 65535.