TypeScript Quick Tips

TypeScript YesJavaScriptsuperset of , added static type option. It can help developers write clearer and easier to maintain code. This article will introduce some practical TypeScript quick tricks to help you master the language faster.

1. Type annotation

Type annotation in TypeScript is a variable,functionThe method of the parameter and return value specifying the type. This helps the compiler understand the intent of the code and provides it at compile timeType Check。

function greet(name: string): string {
  return 'Hello, ' + name;
}

In the example above, wegreetFunction parametersnameSpecified typestring, and also specify a type for the function return valuestring。

2. Interface

Interfaces are a way in TypeScript to define object shapes. It helps you describe the structure of an object and ensures that the object satisfies a specific shape.

interface Person {
  name: string;
  age: number;
}

function greet(person: Person): string {
  return 'Hello, ' + ;
}

In the example above, we define a name calledPersoninterface, it containsnameandageTwo attributes. Then we're ingreetThis interface is used as parameter type in the function.

3. Generics

Generics are a way to create reusable components in TypeScript. It allows you to use type parameters when defining functions, interfaces, or classes, so that you can specify specific types when invoked.

function identity<T>(arg: T): T {
   return arg;
 }

 let output = identity<string>("myString"); // output type is 'string'

In the example above, we define a name calledidentitygeneric function that accepts a type parameterT. CallingidentityWhen functioning, we specify the type parameter asstring, so the type of return value is alsostring。

4. Union type and type alias

Union types allow you to specify that a variable can be one of multiple types. A type alias is to give a new name to a type.

type StringOrNumber = string | number;

function formatValue(value: StringOrNumber): string {
  return typeof value === 'string' ? value : ();
}

In the example above, we define a name calledStringOrNumbertype alias, it can bestringornumbertype. Then we're informatValueThis type alias is used as the parameter type in the function.

5. Enumeration

Enumeration is a way to create named constant collections in TypeScript. It can help you create more readable names for a set of related values or strings.

enum Color {
  Red,
  Green,
  Blue
}

let c: Color = ;

In the example above, we define a name calledColorenumeration, which contains three membersRed、GreenandBlue. Then we create a variablecand assign it to。

6. Assertion

Type assertions in TypeScript are a kind of tellingCompilerThe way the variable is actually typed. This helps you bypass type checking when needed.

let someValue: any = "this is a string";

let strLength: number = (<string>someValue).length;

In the above example, we use type assertion tosomeValueThe variable is asserted asstringtype, then accessed itslengthproperty.

7. Module

Modules in TypeScript are a way to organize code. It allows you to split the code into reusable parts and control their visibility.

 = function greet(name: string): string {
  return 'Hello, ' + name;
};

In the example above, we useExport a name calledgreetfunction.

8. Namespace

Namespaces are another way to organize your code in TypeScript. It allows you to split your code into different namespaces to avoid name conflicts.

namespace Utility {
  export function log(message: string) {
    (message);
  }
}

("Hello, world!");

In the example above, we define a name calledUtilityand export a namespace in it calledlogfunction. Then we passThis function was called.

9. Decorators

Decorators are a way in TypeScript to modify classes and class members. It can help you add extra functionality to classes, methods, properties, or parameters.

function enumerable(value: boolean) {
  return function (target: any, propertyKey: string, descriptor: PropertyDescriptor) {
     = value;
  };
}

class Greeter {