String.prototype.split()
The split()
method divides a
String
into an ordered list of substrings, puts these substrings into an
array, and returns the array. The division is done by searching for a pattern; where
the pattern is provided as the first parameter in the method's call.
Syntax
split()
split(separator)
split(separator, limit)
Parameters
separator
Optional-
The pattern describing where each split should occur. The
separator
can be a simple string or it can be a regular expression.-
The simplest case is when
separator
is just a single character; this is used to split a delimited string. For example, a string containing tab separated values (TSV) could be parsed by passing a tab character as the separator, like this:myString.split("\t")
. -
If
separator
contains multiple characters, that entire character sequence must be found in order to split. -
If
separator
is omitted or does not occur instr
, the returned array contains one element consisting of the entire string. -
If
separator
appears at the beginning (or end) of the string, it still has the effect of splitting. The result is an empty (i.e. zero length) string, which appears at the first (or last) position of the returned array. -
If
separator
is an empty string (""
),str
is converted to an array of each of its UTF-16 "characters".
Warning: When the empty string (
""
) is used as a separator, the string is not split by user-perceived characters (grapheme clusters) or unicode characters (codepoints), but by UTF-16 codeunits. This destroys surrogate pairs. See "How do you get a string to a character array in JavaScript?" on StackOverflow. -
The simplest case is when
limit
Optional-
A non-negative integer specifying a limit on the number of substrings to be included in the array. If provided, splits the string at each occurrence of the specified
separator
, but stops whenlimit
entries have been placed in the array. Any leftover text is not included in the array at all.-
The array may contain fewer entries than
limit
if the end of the string is reached before the limit is reached. - If
limit
is0
,[]
is returned.
-
The array may contain fewer entries than
Return value
An Array
of strings, split at each point where the
separator
occurs in the given string.
Description
When found, separator
is removed from the string, and the
substrings are returned in an array.
If separator
is a regular expression with capturing
parentheses, then each time separator
matches, the results
(including any undefined
results) of the capturing parentheses are spliced
into the output array.
If the separator is an array, then that Array is coerced to a String and used as a separator.
Examples
Using split()
When the string is empty and no separator is specified, split()
returns an array containing one empty
string, rather than an empty array. If the string and separator are both empty
strings, an empty array is returned.
const emptyString = '';
// string is empty and no separator is specified
console.log(emptyString.split());
// [""]
// string and separator are both empty strings
console.log(emptyString.split(emptyString));
// []
The following example defines a function that splits a string into an array of strings
using separator
. After splitting the string, the function logs
messages indicating the original string (before the split), the separator used, the
number of elements in the array, and the individual array elements.
function splitString(stringToSplit, separator) {
const arrayOfStrings = stringToSplit.split(separator)
console.log('The original string is: ', stringToSplit)
console.log('The separator is: ', separator)
console.log('The array has ', arrayOfStrings.length, ' elements: ', arrayOfStrings.join(' / '))
}
const tempestString = 'Oh brave new world that has such people in it.'
const monthString = 'Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dec'
const space = ' '
const comma = ','
splitString(tempestString, space)
splitString(tempestString)
splitString(monthString, comma)
This example produces the following output:
The original string is: "Oh brave new world that has such people in it." The separator is: " " The array has 10 elements: Oh / brave / new / world / that / has / such / people / in / it. The original string is: "Oh brave new world that has such people in it." The separator is: "undefined" The array has 1 elements: Oh brave new world that has such people in it. The original string is: "Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dec" The separator is: "," The array has 12 elements: Jan / Feb / Mar / Apr / May / Jun / Jul / Aug / Sep / Oct / Nov / Dec
Removing spaces from a string
In the following example, split()
looks for zero or more spaces, followed
by a semicolon, followed by zero or more spaces—and, when found, removes the spaces and
the semicolon from the string. nameList
is the array returned as a result
of split()
.
const names = 'Harry Trump ;Fred Barney; Helen Rigby ; Bill Abel ;Chris Hand '
console.log(names)
const re = /\s*(?:;|$)\s*/
const nameList = names.split(re)
console.log(nameList)
This logs two lines; the first line logs the original string, and the second line logs the resulting array.
Harry Trump ;Fred Barney; Helen Rigby ; Bill Abel ;Chris Hand [ "Harry Trump", "Fred Barney", "Helen Rigby", "Bill Abel", "Chris Hand", "" ]
Returning a limited number of splits
In the following example, split()
looks for spaces in a string and returns
the first 3 splits that it finds.
const myString = 'Hello World. How are you doing?'
const splits = myString.split(' ', 3)
console.log(splits)
This script displays the following:
["Hello", "World.", "How"]
Splitting with a RegExp
to include parts of the separator in the result
If separator
is a regular expression that contains capturing
parentheses (
)
, matched results are included in the array.
const myString = 'Hello 1 word. Sentence number 2.'
const splits = myString.split(/(\d)/)
console.log(splits)
This script displays the following:
[ "Hello ", "1", " word. Sentence number ", "2", "." ]
Note: \d
matches the character class for digits between 0 and 9.
Reversing a String using split()
Warning: This is not a robust way to reverse a string:
const str = 'asdfghjkl'
const strReverse = str.split('').reverse().join('')
// 'lkjhgfdsa'
// split() returns an array on which reverse() and join() can be applied
It doesn't work if the string contains grapheme clusters, even when using a unicode-aware split. (Use, for example, esrever instead.)
const str = 'mañana mañana'
const strReverse = str.split('').reverse().join('')
// => "anãnam anañam" // notice how the first word has an ã rather ñ
Bonus: use ===
operator to test if the original string was a
palindrome.
Specifications
Specification |
---|
ECMAScript Language Specification # sec-string.prototype.split |
Browser compatibility
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