当前位置：首页 > article >正文

js,ts控制流程

article 2025/2/23 10:44:17

在这里插入图片描述
摘要：

在 JavaScript 和 TypeScript 中，控制流程是指程序执行的顺序和条件判断。以下是一些常见的控制流程结构，包括条件语句、循环语句和函数调用等。

1. 条件语句：
if 语句

let condition = true;

if (condition) {
  console.log('Condition is true');
} else {
  console.log('Condition is false');
}

switch 语句

let value = 2;

switch (value) {
  case 1:
    console.log('Value is 1');
    break;
  case 2:
    console.log('Value is 2');
    break;
  default:
    console.log('Value is not 1 or 2');
}

2. 循环语句：
for 循环

for (let i = 0; i < 5; i++) {
  console.log(i);
}

while 循环

let i = 0;
while (i < 5) {
  console.log(i);
  i++;
}

do…while 循环

let i = 0;
do {
  console.log(i);
  i++;
} while (i < 5);

for…of 循环

let array = [1, 2, 3, 4, 5];
for (let item of array) {
  console.log(item);
}

for…in 循环

let obj = { a: 1, b: 2, c: 3 };
for (let key in obj) {
  console.log(key, obj[key]);
}

3. 函数调用：
声明函数

function greet(name) {
  console.log(`Hello, ${name}!`);
}

greet('Alice');

箭头函数

const greet = (name) => {
  console.log(`Hello, ${name}!`);
};

greet('Alice');

4. 异步控制流程：
Promise

let promise = new Promise((resolve, reject) => {
  setTimeout(() => {
    resolve('Success');
  }, 1000);
});

promise.then((result) => {
  console.log(result);
}).catch((error) => {
  console.error(error);
});

async/await

async function fetchData() {
  try {
    let response = await fetch('https://api.example.com/data');
    let data = await response.json();
    console.log(data);
  } catch (error) {
    console.error(error);
  }
}

fetchData();

5. 类和对象：
类

class Person {
  name: string;
  age: number;

  constructor(name: string, age: number) {
    this.name = name;
    this.age = age;
  }

  greet() {
    console.log(`Hello, my name is ${this.name} and I am ${this.age} years old.`);
  }
}

let person = new Person('Alice', 30);
person.greet();

对象字面量

let person = {
  name: 'Alice',
  age: 30,
  greet: function() {
    console.log(`Hello, my name is ${this.name} and I am ${this.age} years old.`);
  }
};

person.greet();

6. 错误处理：
try…catch

try {
  // 可能会抛出错误的代码
  throw new Error('Something went wrong');
} catch (error) {
  console.error(error.message);
} finally {
  console.log('This will always run');
}

7. 条件运算符：
三元运算符

let age = 20;
let message = age >= 18 ? 'Adult' : 'Minor';
console.log(message);

8. 数组和对象的方法：
数组方法

let array = [1, 2, 3, 4, 5];

array.forEach((item) => {
  console.log(item);
});

let filteredArray = array.filter((item) => item > 2);
console.log(filteredArray);

let mappedArray = array.map((item) => item * 2);
console.log(mappedArray);

let reducedValue = array.reduce((acc, item) => acc + item, 0);
console.log(reducedValue);

对象方法

let obj = { a: 1, b: 2, c: 3 };

Object.keys(obj).forEach((key) => {
  console.log(key, obj[key]);
});

Object.values(obj).forEach((value) => {
  console.log(value);
});

Object.entries(obj).forEach(([key, value]) => {
  console.log(key, value);
});