Kevin Powell - Community•2y ago

Typeof question

why this is coming out as an object?

let person = ["cheese", "hot"]; console.log(typeof person === "object"); <---- true console.log(this is any array? ${typeof person === "array"}); <---- false``

5 Replies

13eck•2y ago

Because everything in JavaScript is an object :p Also, if you use three backticks (```) it'll give you code blocks (see #How To Ask Good Questions for more on codeblocks). More specifically, anything that's not considered a primitive data type is a typeof object. The following are primitive data types (those that are passed by value and not by reference) • string • number • bigint • boolean • undefined • symbol • null If you want to know what exact type something is, you can use this snippet:

Object.prototype.toString.call("insert data here").slice(8, -1).toLowerCase()

Object.prototype.toString.call("insert data here").slice(8, -1).toLowerCase()

The Object.prototype.toString.call([data]) will give you [Object [Type]] and the slice grabs just the type and makes it lowercase.

Object.prototype.toString.call("insert data here").slice(8, -1).toLowerCase() // returns "string"
Object.prototype.toString.call([1,2,3]).slice(8, -1).toLowerCase() // returns "array"
Object.prototype.toString.call({hello: "world"}).slice(8, -1).toLowerCase() // returns "object"
// …etc, etc, etc

Object.prototype.toString.call("insert data here").slice(8, -1).toLowerCase() // returns "string"
Object.prototype.toString.call([1,2,3]).slice(8, -1).toLowerCase() // returns "array"
Object.prototype.toString.call({hello: "world"}).slice(8, -1).toLowerCase() // returns "object"
// …etc, etc, etc

Ali•2y ago

@interactive-harp or if want to just check if it is an array or not you can use Array.isArray(person)

interactive-harp•2y ago

thanks, another question this is my array:

let person = ["cheese", "hot"];

let plea = "wouldShe";

person.name = "Mr. White";

person.plea = plea;

person["diary"] = "diary"; 

console.log(person);

console.log(person.length) This is the output: [ 'cheese', 'hot',
name: 'Mr. White', plea: 'wouldShe', diary: 'diary' ] 2 length is 2, shouldn't it be 5?

13eck•2y ago

The actual output is:

13eck•2y ago

The length is 2 because that's how many items are in the array Remember that everything in JS is an object, so your array now also has some object keys/values in addition the the 2 items in the array (and that's all that .length measures, the number of items in the array) The items prefixed with a number are the array indexes. This is digging into the weeds a bit, but when they say everything is an object everything is an object. An array isn't actually an array, it's an object with a length property and each item in the "array" is a property on the "array" object with a key of the "array" index Also, please use code blocks instead of inlining the formatting like that Start you code blocks with this: ```javascript // code goes here ``` And you can replace javascript with almost any programming language to use appropriate text highlighting (on desktop). Like HTML, CSS, Go, Python, etc.

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