current position：Home>[front end interview question] es variable type (type classification, type judgment, value type and reference type)
[front end interview question] es variable type (type classification, type judgment, value type and reference type)
2022-01-27 03:34:09 【Erlin loves meat】
The variable type part is mainly divided into two points ：
- JS Data type classification and type judgment
- Value type and reference type
ES It defines 6 Primitive types ：
JS As defined in 8 Type of data ：
among Symbol and BigInt yes ES6 New data types .
Symbol It mainly solves the problem of possible global variable conflict .
BigInt It's a digital type of data , It can represent an integer of any precision , We use bigint It can safely store and operate integers .
How to determine the type of data ：
typeof The resulting value may be Undefined、boolean、number、string、Object、function、Symbol
It should be noted that ：typeof(null)、typeof(array) All the results are object.
instanceof You can solve it typeof Can't judge the problem of array , however instanceof There are also shortcomings. , Can't distinguish null and Undefined.
It was written before js Several ways to determine the type of data , There is a detailed explanation , The attached code , Interested readers can have a look ：
Value type and reference type
Value types include ：
Reference types include ：
There is a simpler classification of reference types ： Array 、 object 、 function
Difference between value type and reference type ：
Different storage locations ： Value types are stored in the stack , The address of the reference type exists in the stack , Values are stored in the heap .
Is the value variable ： Value type （ Basic types ） Once the value of the variable is determined, it is immutable , But the value of the reference type is variable .
author[Erlin loves meat],Please bring the original link to reprint, thank you.
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