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.
isArray() method is used to check if an object is an array. The Array. isArray() method returns true if an object is an array, otherwise returns false .
Answer: Use the Array. isArray() Method isArray() method to check whether an object (or a variable) is an array or not. This method returns true if the value is an array; otherwise returns false .
Both objects and arrays are considered “special” in JavaScript. Objects represent a special data type that is mutable and can be used to store a collection of data (rather than just a single value). Arrays are a special type of variable that is also mutable and can also be used to store a list of values.
You shouldn't use the typeof operator to check whether a value is an array, because typeof cannot distinguish between arrays and objects. Instead you should use Array. isArray() , because typeof would return 'object' , not 'array' . Array.
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.
_.isArray // underscore method.
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.
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