How can I check if an object is an array?

Question

I'm trying to write a function that either accepts a list of strings, or a single string. If it's a string, then I want to convert it to an array with just the one item so I can loop over it without fear of an error. So how do I check if the variable is an array?

Accepted Answer

In modern browsers you can do:

```
Array.isArray(obj)
```

(Supported by Chrome 5, Firefox 4.0, Internet Explorer 9, Opera 10.5 and Safari 5)

For backward compatibility you can add the following:

```
// Only implement if no native implementation is available
if (typeof Array.isArray === 'undefined') {
  Array.isArray = function(obj) {
    return Object.prototype.toString.call(obj) === '[object Array]';
  }
};
```

If you use jQuery you can use `jQuery.isArray(obj)` or `$.isArray(obj)`. If you use Underscore.js you can use `_.isArray(obj)`.

If you don't need to detect arrays created in different frames you can also just use `instanceof`:

```
obj instanceof Array
```

How can I check if an object is an array?

Solution

Problem

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