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Typescript advanced
2021-08-26 00:47:28 【forever_ Mamba】
This is my participation 8 The fourth of the yuegengwen challenge 22 God , Check out the activity details :8 Yuegengwen challenge
Preface
“ The color of August is made of gold , Bright and precious ; The color of August is brewed by sunshine , Fragrant and brilliant .”
The days ahead , May you adjust yourself to your best , Work slowly , Slowly getting better Y(^o^)Y
Type the alias
Type aliases are used to give a type a new name , Commonly used for union types
type Name = string;
type NameResolver = () => string;
type NameOrResolver = Name | NameResolver;
function getName(n: NameOrResolver): Name {
if (typeof n === 'string') {
return n;
} else {
return n();
}
}
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String literal type
String literal type is used to restrict that the value can only be one of several strings
type EventNames = 'click' | 'scroll';
function handleEvent(ele: Element, event: EventNames) {
// todo
}
handleEvent(document.getElementById('hello'), 'scroll'); // That's all right.
handleEvent(document.getElementById('world'), 'dblclick'); // Report errors ,event Not for 'dblclick'
// index.ts(7,47): error TS2345: Argument of type '"dblclick"' is not assignable to parameter of type 'EventNames'.
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Type alias and string literal type are both used type Define
Tuples
Tuples (Tuple) Merging different types of objects
Define a pair of values as string
and number
tuples .= let tom: [string, number] = ['Tom', 25];
This definition limits the type of each element in the array , in other words tom[0]
It has to be for string
,tom[1]
It has to be for number
.
If you add a new out of bounds element to the array , The data type of the new element can be any type of the time ancestor
tom.push('jarry');
tom.push(true);
// Argument of type 'true' is not assignable to parameter of type 'string | number'.
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enumeration
enumeration (Enum
) Type is used for scenarios where the value is limited to a certain range , For example, a week can only have seven days , The color is limited to red, green and blue . Enumerations are usually used to define some keywords .
enum Days {Sun, Mon, Tue, Wed, Thu, Fri, Sat};
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Interface inherits interface
Interface (Interfaces
) It can be used for 「 The shape of the object (Shape
)」 Describe
Interfaces can be inherited between interfaces
interface Alarm {
alert(): void;
}
interface LightableAlarm extends Alarm {
lightOn(): void;
lightOff(): void;
}
LightableAlarm Inherited Alarm, Besides having alert Out of the way , There are also two new methods lightOn and lightOff
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Generic
Generic (Generics
) It means defining functions 、 Interface or class , Do not specify specific types in advance , And when you use it, you specify a feature of type
function createArray<T>(length: number, value: T): Array<T> {
let result: T[] = [];
for (let i = 0; i < length; i++) {
result[i] = value;
}
return result;
}
You can specify its specific type as string
createArray<string>(3, 'x'); // ['x', 'x', 'x']
You can not specify it manually , And let the type inference work out automatically
createArray(3, 'x'); // ['x', 'x', 'x']
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We added... After the function name <T>
, among T
Used to refer to any type of input , Input at the back value: T
And the output Array<T>
You can use
Conclusion
If this article helps you , Welcome to praise and concern ️.
If there are mistakes in the article , Hope to correct in the comment area .
copyright notice
author[forever_ Mamba],Please bring the original link to reprint, thank you.
https://en.qdmana.com/2021/08/20210826004726099j.html
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