How should I detect if the argument is an array because typeof []
returns 'object'
and I want to distinguish between arrays and objects.
It is possible that object will look like {"0":"string","1":"string","length":"2"}
but I don't want it to come out as an array if it is in fact an object looking like an array.
JSON.parse
and JSON.stringify
are able to make this distinction. How can I do it?
I am using Node.JS which is based on V8 the same as Chrome.
Array.isArray
native V8 function. It's fast, it's always correct. This is part of ES5.
arr instanceof Array
Checks whether the object was made with the array constructor.
A method from underscore. Here is a snippet taken from the their source
var toString = Object.prototype.toString,
nativeIsArray = Array.isArray;
_.isArray = nativeIsArray || function(obj) {
return toString.call(obj) === '[object Array]';
};
This method takes an object and calls the Object.prototype.toString
method on it. This will always return [object Array]
for arrays.
In my personal experience I find asking the toString
method is the most effective but it's not as short or readable as instanceof Array
nor is it as fast as Array.isArray
but that's ES5 code and I tend to avoid using it for portability.
I would personally recommend you try using underscore
, which is a library with common utility methods in it. It has a lot of useful functions that DRY up your code.