javascript - what array is this?

Question

When I was learning regular expressions, I found that the exec method returned such an array. What kind of array is this?

I entered this array in the browser console and found an error

Answer 1

My typeof looks at it and it says it is an object, but typeof checks the data and will tell you it is an object.

I used Array.isArray to check again and it returned true.

So I took a look at the explanation of this function on MDN:

https://developer.mozilla.org...

It says the return value is an array.

I took a look at ECMA 5.1 and couldn’t find any description of arrays above

http://ecma-international.org...

So I am also here waiting for the master to answer =. =

----------------- The dividing line for forced explanation ------------------

An instance of an array is also an object, so you can indeed add properties and assign values ​​to it.

But please note that for variables that are not composite types, there is no way to add attributes and assign values ​​to their instances. Because it’s useless even if you do it.

I misremembered, so I thought there was no way to add attribute assignments to numerical instances. . . . .

Answer 2

let a = ["Box"];
a.index = 10;
a.input = "This is a Box! That is a Box!";

Answer 3

Although the regular exec return value is an array, it has other attributes. For details, please refer to the documentation. Please read more in Rhinoceros or Height.

Answer 4

var a = [];
a[0] = 'tets'
a[1] = 'fasfasf'
a.index = '对象属性'

Output a Get, in JavaScript, an array is also an object

["tets", "fasfasf", index: "hahaha"]

Answer 5

My understanding is the members of the array and the members on the array object.
]

Answer 6

var a={0:"Box"};
a.index=10;
a.input="This is a Box! That is a Box!";
var b=["Box"];
b.index=10;
b.input="This is a Box! That is a Box!"
console.log(a,b);

In fact, the most confusing thing here is, why can ["Box"].index=10 be set successfully?
Look at the print results first:

To illustrate it more clearly, we expand it and observe its prototype chain.
Prototype chain of object a:

Prototype chain of array b:

As can be seen from the above figure, the array inherits the methods of the Object type from the prototype chain.
When ["box"] cannot find the corresponding method in Array(0), it will go down the prototype chain to find the method in Object.
So theoretically, the array type can also be considered a type of object type.

Answer 7

var a = ['box'];
a.index = 'dsfsaf';
a.input = 'gfhdsgsadreqw';
console.log(a)

Answer 8

The first question: It’s just an ordinary array

Second question: Grammar error

[] 定义数组