JavaScript 代码示例的 Dart 对应代码

2024-01-16 04:51:30

概述

作为一名开发过 React/React Native 的工程师，在刚开始接触 Flutter 开发时，难免会遇到这样的情况：对于某个功能，您可以很熟练地使用特定的 JavaScript 语法来完成，但对于 Flutter 开发，却不知该如何下手。

本文将提供 15 个 JavaScript 代码示例及其对应的 Dart 代码，帮助您轻松过渡到 Flutter 开发，提高您的编码效率。这些示例涵盖了从基本数据类型到高级函数的使用，旨在帮助您快速掌握 Flutter 开发的技巧和最佳实践。

JavaScript 代码示例及其 Dart 对应代码

1. 变量声明和类型注释

JavaScript

let name = 'John Doe';

Dart

String name = 'John Doe';

2. 常量声明

JavaScript

const PI = 3.14159265359;

Dart

const double PI = 3.14159265359;

3. 算术运算符

JavaScript

let sum = 1 + 2;

Dart

int sum = 1 + 2;

4. 比较运算符

JavaScript

if (a > b) {
  // Do something
}

Dart

if (a > b) {
  // Do something
}

5. 逻辑运算符

JavaScript

if (a && b) {
  // Do something
}

Dart

if (a && b) {
  // Do something
}

6. 数组声明和访问

JavaScript

let array = [1, 2, 3];

Dart

List<int> array = [1, 2, 3];

7. 循环语句

JavaScript

for (let i = 0; i < array.length; i++) {
  // Do something
}

Dart

for (int i = 0; i < array.length; i++) {
  // Do something
}

8. 函数声明

JavaScript

function sum(a, b) {
  return a + b;
}

Dart

int sum(int a, int b) {
  return a + b;
}

9. 箭头函数

JavaScript

const sum = (a, b) => a + b;

Dart

int sum(int a, int b) => a + b;

10. 类声明

JavaScript

class Person {
  constructor(name) {
    this.name = name;
  }

  greet() {
    console.log(`Hello, my name is ${this.name}.`);
  }
}

Dart

class Person {
  String name;

  Person(this.name);

  void greet() {
    print('Hello, my name is $name.');
  }
}

11. 继承

JavaScript

class Student extends Person {
  constructor(name, major) {
    super(name);
    this.major = major;
  }

  study() {
    console.log(`I am studying ${this.major}.`);
  }
}

Dart

class Student extends Person {
  String major;

  Student(String name, this.major) : super(name);

  void study() {
    print('I am studying $major.');
  }
}

12. 接口

JavaScript

interface Drawable {
  draw();
}

Dart

abstract class Drawable {
  void draw();
}

13. 泛型

JavaScript

function map(array, callback) {
  let result = [];
  for (let i = 0; i < array.length; i++) {
    result.push(callback(array[i]));
  }
  return result;
}

Dart

List<T> map<T>(List<E> array, T Function(E) callback) {
  List<T> result = [];
  for (E element in array) {
    result.add(callback(element));
  }
  return result;
}

14. 异步编程

JavaScript

async function fetchUserData() {
  const response = await fetch('https://example.com/api/users');
  const data = await response.json();
  return data;
}

Dart

Future<List<User>> fetchUserData() async {
  final response = await http.get('https://example.com/api/users');
  if (response.statusCode == 200) {
    return json.decode(response.body) as List<User>;
  } else {
    throw Exception('Failed to fetch user data.');
  }
}

15. 状态管理

JavaScript

import { useState } from 'react';

function MyComponent() {
  const [count, setCount] = useState(0);

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>
    </div>
  );
}

Dart

import 'package:flutter/material.dart';

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  int count = 0;

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Text('Count: $count'),
        ElevatedButton(
          onPressed: () => setState(() => count++),
          child: Text('Increment'),
        ),
      ],
    );
  }
}