String.prototype.includes()
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2015.
The includes()
method of String
values performs a case-sensitive search to determine whether a given string may be found within this string, returning true
or false
as appropriate.
Try it
Syntax
includes(searchString)
includes(searchString, position)
Parameters
searchString
-
A string to be searched for within
str
. Cannot be a regex. All values that are not regexes are coerced to strings, so omitting it or passingundefined
causesincludes()
to search for the string"undefined"
, which is rarely what you want. position
Optional-
The position within the string at which to begin searching for
searchString
. (Defaults to0
.)
Return value
true
if the search string is found anywhere within the given string, including when searchString
is an empty string; otherwise, false
.
Exceptions
TypeError
-
Thrown if
searchString
is a regex.
Description
This method lets you determine whether or not a string includes another string.
Case-sensitivity
The includes()
method is case sensitive. For example, the following expression returns false
:
"Blue Whale".includes("blue"); // returns false
You can work around this constraint by transforming both the original string and the search string to all lowercase:
"Blue Whale".toLowerCase().includes("blue"); // returns true
Examples
Using includes()
const str = "To be, or not to be, that is the question.";
console.log(str.includes("To be")); // true
console.log(str.includes("question")); // true
console.log(str.includes("nonexistent")); // false
console.log(str.includes("To be", 1)); // false
console.log(str.includes("TO BE")); // false
console.log(str.includes("")); // true
Specifications
Specification |
---|
ECMAScript Language Specification # sec-string.prototype.includes |
Browser compatibility
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