js,ts控制流程

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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);
});