JavaScript Strings
Updated: June 21, 2020A string is a series of zero or more characters grouped together inside single or double quotes.
In order to define a string
, we must do it by starting and ending with either single or double quotes.
Problems, however, might arise, if we have to include a literal quote "
or '
inside the string
:
The code above will generate an error on the console: Uncaught SyntaxError: Unexpected identifier
, since JavaScript doesn't know where the string variable ends.
To fix this problem, we can escape the quote from being considered as the end of the string quote by using the backslash \
in front of the quote:
JavaScript supports both single and double quotes, as long as we start and end the string variable with the same type of quotes. Moreover, we can fix the issue of using a literal quote inside a string variable, thanks to the backslash \
character.
It's important to not abuse backslash \
character; since it can make our code more difficult to read.
For this reason, we can always use single quotes for our string variables and use double quote only when needed inside the variable, like in the code below:
Escape Sequences in Strings
Other than quotes, in JavaScript, we can escape many other characters inside a string. The main reason to do this is to use multiple quotes in a string without JavaScript misinterpreting our code.
Example:
Concatenating Strings with Plus Operator
In JavaScript, however, we can use the +
operator also inside a String
value, and in that case it's called concatenation operator
.
This operator is very helpful to concatenate together multiple strings in order to build a new one.
Concatenating Strings with the Plus Equals Operator
We can concatenate strings together also by using the +=
operator.
This practice can be very helpful if we have to break a long string over several lines or to perform string manipulations using JavaScript.
Constructing Strings with Variables
The +
operator can be used not only to concatenate Strings
, but also to build a new string by inserting one or more variables into it.
Appending Variables to Strings
We can append variables to a string using the plus equals +=
operator.
Find the Length of a String
If we want to calculate the length of a String
, we can write .length
at the end of the string variable or string literal.
Use Bracket Notation to Find the First Character in a String
In JavaScript, we use bracket notation
to get a character at a specific index within a string. Moreover, instead of starting to count at 1, we start at 0. This is referred to as Zero-based indexing
.
For example, the character at index 0 in the word "Charles" is "C". So if var firstName = "Charles"
, you can get the value of the first letter of the string by using firstName[0]
.
Understand String Immutability
In JavaScript, String
are immutable
. This means that they cannot be modified once created.
For instance:
As we can see from the code above, String immutability
doesn't mean that the string variable cannot be changed, just that the single individual character of a string literal
cannot be changed.
That's why the only way we can change myStringVariable
is to assign it with a completely new string:
Use Bracket Notation to Find the Nth Character in a String
We can use bracket notation
also to get a particular character's position within a string.
Use Bracket Notation to Find the Last Character in a String
Bracket Notation allows us to make also some basic logic and find the last letter of a string. We can do it by subtracting one from the string's length.
Use Bracket Notation to Find the Nth-to-Last Character in a String
In the same way we calculated the last character in a string, we can retrieve also the Nth-to-last character.