Why does `typeof` return \'object\' for arrays of objects in JavaScript?

Examination of the Unique JavaScript Behavior: Why Arrays of Objects Return "object" Instead of "array"

In JavaScript, an intriguing phenomenon arises when working with arrays of objects. Surprisingly, despite their array-like nature, they are classified as objects when the typeof operator is employed. This discrepancy can be quite perplexing, especially in cases like the below:

$.ajax({
    url: 'http://api.twitter.com/1/statuses/user_timeline.json',
    data: { screen_name: 'mick__romney'},
    dataType: 'jsonp',
    success: function(data) {
        console.dir(data); //Array[20]
        alert(typeof data); //Object
    }
});​

This behavior stems from a peculiarity in the JavaScript specification that considers Array objects to be of type Object. However, this does not imply that arrays and objects are interchangeable. To accurately determine whether a variable represents an array, employ the following methods:

• instanceof Array: Checks if a variable is an instance of the Array constructor.
• Array.isArray(data): A native method specifically designed to determine if a variable is an array.
• Object.prototype.toString.call(data) == '[object Array]': A reliable approach that utilizes the toString method of the Object prototype.
• jQuery.isArray(data): A convenient option for jQuery users.

By utilizing these techniques, you can precisely discern whether a variable is an array, even when it contains objects, resolving the apparent discrepancy between its array-like behavior and object classification.

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