How do I make a JavaScript array that has properties?

Question

The RegExp.exec function returns something that looks like a hybrid array. It's an array, but it has properties.

console.log(/d(b+)(d)/i.exec("cdbBdbsbz"));
// => ["dbBd", "bB", "d", index: 1, input: "cdbBdbsbz"]

I can call result[0], result[1], result.index, result.input, etc.

How do I make my own?

[0, 1, "a": 1] is obviously a syntax error, and {"0": 1, "1": 1, "a": 1} does give me an object I can index and access properties of, however it's not the same as what's returned by exec.

I tried doing it with __proto__:

arr = [1, 2, 3];
arr.__proto__.a = 1 // arr.a is 1 now

But console.log doesn't display the property like it does when run on the result of exec, so I suspect it's still not the same thing.

Jamiec · Accepted Answer · 2012-11-26 10:24:12Z

5

Easy enough - an array in javascript is just an object, and you can attach any properties you like to it:

var test = ["foo","bar","baz"];
test.index = 1;
test.input="foobarbaz";
console.log(test);

That console.log looks identical to the one returned by regex.exec.

Live example: http://jsfiddle.net/9rCmJ/

answered Nov 26, 2012 at 10:24

Jamiec

136k15 gold badges143 silver badges202 bronze badges

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

Comments

Álvaro González · Accepted Answer · 2012-11-26 10:21:14Z

3

Do you mean this?

var arr = [0, 1];
arr.a = 1;

answered Nov 26, 2012 at 10:21

Álvaro González

147k45 gold badges282 silver badges378 bronze badges

Comments

luin · Accepted Answer · 2012-11-26 10:23:47Z

3

An array is also an object, so you can set property directly:

var myArray = ['a', 'b'];
console.log(typeof myArray); // 'object'
myArray.say = 'hi';

answered Nov 26, 2012 at 10:23

luin

1,9952 gold badges20 silver badges25 bronze badges

Comments

sphair · Accepted Answer · 2012-11-26 10:24:29Z

3

Do it in two steps:

var a = [1, 2, 3];
a.test = "Hello world";

answered Nov 26, 2012 at 10:24

sphair

1,67015 silver badges29 bronze badges

Collectives™ on Stack Overflow

How do I make a JavaScript array that has properties?

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related