Cast string as array

Question

How, in Javascript, can I cast a string as an array in the same way that PHP (array) does.

//PHP
$array = (array)"string"

Basically I have a variable that can be an array or a string and, if a string, I want to make it an array using an inline command.

Answer - Using the selected answer with the more recent Array.flat() we can do:

let foo = 'foo'
let bar = ['foo']

[foo].flat() // ['foo']
[bar].flat() // ['foo']

It does require wrapping in brackets but does cast as array only if necessary in one go without ternary.

There is casting in JS but it is seldom used (just like in PHP). A common use is to treat a number as a string or a string as a number. "1" + "1" = "11" if you are not careful. — Levi Botelho
– Levi Botelho, Commented Oct 27, 2012 at 18:29
You want to make it an Array of what? Should it be an Array of individual characters in the string? Or an Array that has the entire string at its first index? — I Hate Lazy
– I Hate Lazy, Commented Oct 27, 2012 at 18:34

Pedro Nascimento · Accepted Answer · 2013-09-27 19:36:10Z

42

Hacky, but works:

[].concat(arrayOrString);

//Usage:
[].concat("a");
//["a"]
[].concat(["a"]);
//["a"]

answered Sep 27, 2013 at 19:36

Pedro Nascimento

14.1k4 gold badges38 silver badges64 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Metalstorm Over a year ago

[Note] This is rather slow compared to the alternative: jsperf.com/array-coerce

jeromej Over a year ago

@Metalstorm Was it used in the same way? jsperf is currently down and I cannot check.

Enrico Over a year ago

@JeromeJ yes, it compares concat with Array.isArray(). The difference is noticeable.

jeromej Over a year ago

@Zim Ah thanks! Way faster indeed but sadly less beautiful: Array.isArray(obj) ? obj:[obj]

Kerry Johnson Over a year ago

This was the only solution I could find that would allow me to transform a string property to array inside a foreach statement. ([].concat(foo.bar.stringOrArray)).forEach((item) => {...})

Yanick Rochon · Accepted Answer · 2022-04-28 14:17:51Z

29

JavaScript is a prototyping language and does not have a type casting system.

One solution would be to check if your variable is a string and convert it into an array. For example :

if (typeof someVariable === 'string') someVariable = [someVariable];

In PHP, if you do a check on a string, like (ex: $array = 'string';) :

$array = (array) $array;  // ex: "string" becomes array("string")

The JavaScript equivalent will be

arr = typeof arr === 'string' ? [arr] : arr;

If your variable arr is not necessarily a string, you may use instanceof (edit: or Array.isArray) :

arr = arr instanceof Array ? arr : [arr];
arr = Array.isArray(arr) ? arr : [arr];

edited Apr 28, 2022 at 14:17

answered Oct 27, 2012 at 18:29

Yanick Rochon

53.8k30 gold badges147 silver badges232 bronze badges

Comments

Andre Meinhold · Accepted Answer · 2012-10-27 18:27:32Z

7

var str    = "string";
var array  = str.split('');

console.log(array); // ['s', 't', 'r', 'i','n','g']

answered Oct 27, 2012 at 18:27

Andre Meinhold

5,3354 gold badges23 silver badges30 bronze badges

4 Comments

Yanick Rochon Over a year ago

in PHP doing str = (array)"string" results in array("string") not array('s','t','r','i','n','g').

MrHIDEn Over a year ago

Any way I was looking for ['s', 't', 'r', 'i','n','g'] from "string". THX

jeromej Over a year ago

str_split($my_string) in PHP btw.

Tom Auger Over a year ago

If that's what you want (and not what the OP was asking for), then just use Array.from() see MDN notes [developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

Val · Accepted Answer · 2013-08-08 09:03:17Z

4

You can in jQuery...

var arr = "[1,2,3,4,5]"; 
window.x = $.parseJSON(arr);
console.log(x);//cast as an array...

it works even if you have something like

[{"key":"value"}]

However this may NOT work if you have something like this...

[{key:"value"}] // different is the " (double quotes) on key

answered Aug 8, 2013 at 9:03

Val

17.6k24 gold badges99 silver badges148 bronze badges

1 Comment

t.mikael.d Over a year ago

You don't need jQuery for that (Any more) , JSON.parse(arr); works the same.

Don P · Accepted Answer · 2015-03-18 22:36:39Z

3

Turn a string into an array:

var myString = "['boop','top','foo']";
var myArray = JSON.parse(myString)

answered Mar 18, 2015 at 22:36

Don P

64.3k123 gold badges319 silver badges451 bronze badges

Comments

Tom Auger · Accepted Answer · 2024-12-20 05:49:43Z

1

Modern JavaScript now has Array.prototype.flat() which will do the trick.

let a = "a";
let b = "b";

[a].flat(); // result: ["a"]
[[a, b]].flat(); // result ["a", "b"]

This allows you to do this in your function:

function acceptsArrayOrScalar(arrayOrScalar){
   return [arrayOrScalar].flat();
}

acceptsArrayOrScalar(a); // returns [a]
acceptsArrayOrScalar([a, b]); // returns [a, b]

This kind of thing is useful if you want to be able to iterate over your parameter with a for..of or forEach and you don't want to have to do a manual check of isArray() etc.

function doStuff(param){
   [param].flat().forEach(x => console.log(x));
}

doStuff("a"); // logs "a"
doStuff(["a", "b"]); // logs "a" and then "b"

In the contrived example above, you could probably achieve a similar result with the ...rest parameter if all you care about is being able to handle a variable amount of parameters:

function doMoreStuff(...param){
   param.forEach(x => console.log(x));
}

Note though that in this last example, we're not accepting a scalar or an array, we're accepting a variable number of arguments, so it's a slightly different signature, but it might be just what you need.

doMoreStuff("a"); // logs "a"
doMoreStuff("a", "b"); // logs "a" and then logs "b"
doMoreStuff(["a", "b"]); // maybe not what we want: logs ["a", "b"]

And if you want real versatility where you can accept a scalar, or an array, or a variable number of scalars, you could specify the depth parameter:

function doAllTheStuff(...params){
   [params].flat(2).forEach(x => console.log(x));
}

doAllTheStuff("a"); // logs "a"
doAllTheStuff(["a", "b"]); // logs "a" and then "b"
doAllTheStuff("a", "b", "c"); // logs "a", then "b", then "c"

...and even...

doAllTheStuff(["a", "b"], "c"); // logs "a", then "b", then "c"

Arguably, the Array.isArray() ternary is computationally faster, it's unlikely that any production code that uses this trick will suffer significantly, but just be aware of that nuance if inside a game loop or something that needs to be highly performant.

edited Dec 20, 2024 at 5:49

answered Dec 20, 2024 at 4:46

Tom Auger

20.2k23 gold badges87 silver badges109 bronze badges

2 Comments

cyberwombat Feb 5 at 0:40

13 years later I think its time to pick an answer and that's prob as close as we're going to get.

Tom Auger Feb 19 at 15:42

Appreciate it @cyberwombat :)

vyakhir · Accepted Answer · 2012-10-27 18:32:15Z

1

Just do like this

"sample".split("");

and you'll get

["s", "a", "m", ...]

answered Oct 27, 2012 at 18:32

vyakhir

1,8033 gold badges18 silver badges22 bronze badges

1 Comment

jartaud Over a year ago

If you have something like: "[10,20,34,0]" and you want it to be: [10,20,34,0], your solution won't work.

J. K. · Accepted Answer · 2012-10-27 18:29:02Z

0

You cannot cast to Array in JS but a simple ternary operation can do what you want.

var str = 'string';
var arr = (str instanceof Array) ? str : [ str ];

This works for any non-Array object or any primitive value. If you're sure that only actual Array objects and string primitives can be encountered here, the following is a bit faster:

var arr = (typeof str === 'string') ? [ str ] : str;

answered Oct 27, 2012 at 18:29

J. K.

8,3781 gold badge38 silver badges36 bronze badges

2 Comments

jeromej Over a year ago

How does it compare with Array.isArray(str) ? str:[str]?

jeromej Over a year ago

Update: stackoverflow.com/questions/22289727/… > Array.isArray is a bit better.

AnandVeeramani · Accepted Answer · 2012-10-27 18:29:07Z

0

"1,2,3".split(",") 
=> ["1", "2", "3"]

use split()

answered Oct 27, 2012 at 18:29

AnandVeeramani

1,5569 silver badges15 bronze badges

1 Comment

Yanick Rochon Over a year ago

this is not the PHP equivalent asked in the question

Rahul · Accepted Answer · 2013-09-25 18:48:56Z

0

Val's suggestion also works for strings which have array of arrays

var str = "[[1121,1],[1122,2],[1123,3]]";
var arr = $.parseJSON(str);
console.log(arr); //returns array of arrays

answered Sep 25, 2013 at 18:48

Rahul

11 bronze badge

Comments

jcwhall · Accepted Answer · 2017-11-28 10:14:38Z

0

You can also use the following if statement:

if(array instanceof Array != true) {array = [array];}

answered Nov 28, 2017 at 10:14

jcwhall

594 bronze badges

Comments

grantwparks · Accepted Answer · 2021-12-26 01:51:33Z

0

Array.isArray(foo) || (foo = [foo]);

or if that's not comfortable

foo = Array.isArray(foo) ? foo : [foo];

edited Dec 26, 2021 at 1:51

answered Dec 11, 2021 at 17:20

grantwparks

1,1639 silver badges13 bronze badges

Comments

Philipp Kühn · Accepted Answer · 2018-03-25 21:24:26Z

-2

There is already a proposal for Array.flatten() and usable with babel-preset-stage-2.

const array = ['foo'].flatten()
console.log(array) // ['foo']

const array = [['foo', 'bar']].flatten()
console.log(array) // ['foo', 'bar']

answered Mar 25, 2018 at 21:24

Philipp Kühn

1,6592 gold badges20 silver badges26 bronze badges

Collectives™ on Stack Overflow

Cast string as array

13 Answers 13

5 Comments

Comments

4 Comments

1 Comment

Comments

2 Comments

1 Comment

2 Comments

1 Comment

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

13 Answers 13

5 Comments

Comments

4 Comments

1 Comment

Comments

2 Comments

1 Comment

2 Comments

1 Comment

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related