“This is the third day of my participation in the Gwen Challenge in November. Check out the details: The last Gwen Challenge in 2021.”

Front knowledge

Object represents a non-primitive type, that is, a type other than number, string, Boolean, symbol, NULL, or undefined.

Object class

There is no error when we declare it like this

let foo: object = function () {}let foo1: object = []
let foo2: object = { }
Copy the code

But we use it to declare a raw value and get an error

let foo3: object = false / / an error
Copy the code

How do I declare an object?

We can do this by declaring object arguments

let foo = {}
Copy the code

Of course we can add some restrictions

let foo: {name: string, age: number } = {name:'Tom'.age: 11 }
Copy the code

Of course you could write it this way

letfoo: {name? : string,age: number } = {name:'Tom' }
Copy the code

How do you define objects?

In TypeScript, we use Interfaces to define the types of objects. (More on that next time lol)

Array Array type

We can make a statement like this

let list: number[] = [1.2.3];
Copy the code

You can also use array generics

let list: Array<number> = [1, 2, 3];
Copy the code

Both methods represent an array of elements of this type

A tuple type

A tuple type is a special type that I understand to be an array with an explicit element type and number

The basic mold

// Let's define one
let x: [string, number];
Copy the code

The right example

x = ['hello'.10]; // OK
Copy the code

The wrong case

x = [10.'hello']; // Error
Copy the code

or

x = ['hello'.10.10]; // Error
Copy the code

Enumerated type

Enum types complement the JavaScript standard data types.

In JavaScript we often use an object to simulate enumerated classes.

let Status = {
    dangurous: 0.safe: 1,}Copy the code

inTypeScriptHow do you behave in?

enum Color { 
    Red, 
    Green,
    Blue
} 
let c: Color = Color.Green;  / / 1
Copy the code

In the absence of any assignment, number the elements starting at 0 and add up. Using this feature we can also do the following

enum Color { 
    Red = 2, 
    Green,
    Blue
} 
let c: Color = Color.Green;  / / 3
Copy the code

Of course if we do this we will get an error

enum Color { 
    Red = 'red', 
    Green, // Enum member must have initializer.
    Blue // Enum member must have initializer.
} 
let c: Color = Color.Green; 
Copy the code

The main reason for this is that strings don’t grow by themselves, so we need to do a separate assignment

summary

This chapter is mainly and you introduced about the object type below some value operations, after we will give you some classes, interfaces, functions related articles