TypeScript数组和对象的操作

一、数组的声明

let arr1: Array<number>;
let arr2: number[];

二、数组初始化

let arr1: Array<number> = new Array<number>();
let arr2: number[] = [1,2,3];

三、数组元素赋值、添加、更改

// 基本变量不需要声明后可以不需要初始化；
let a:number;
a = 1;
console.log(a); // 1let b: string;
b = "string";
console.log(b); // string// 数组和对象使用之前必须要初始化；
let arr1: Array<number>;
// arr1[0] = 100; // Variable 'arr1' is used before being assigned.
//arr1.push(100);  // 就算使用push来添加也不行
//console.log(arr1)let arr2: Array<number> = new Array<number>();
arr2[0] = 1;  // 赋值和修改格式一样
arr2.push(2);	// 最后面增加,可以多个值
arr2.unshift(3) // 最前面增加，可以多个值
console.log(arr2)  // [3, 1, 2, 3] 

四、删除

let arr: Array<number> = [1,2,3,4,5]
arr.pop();
console.log(arr);   // [1, 2, 3, 4] arr.shift();
console.log(arr);   // [2, 3, 4] arr.splice(0,2);     // 删除元素（index, deleteCount）
console.log(arr);    // [4] 

五、合并、断开数组

let arr: Array<number> = [1,2,3]
let arr2: Array<number> = [4,5,6]
let arrValue = 7arr = arr.concat(arr2)console.log(arr) //[1, 2, 3, 4, 5, 6] arr = arr.concat(arrValue)console.log(arr) //[1, 2, 3, 4, 5, 6, 7] let newArray = arr.slice(1, 3)
console.log(newArray)  // [2,3]

六、查找数组元素

let arr: Array<string> = ["a", "b", "c", "d"]let index = arr.indexOf("c") //返回查找到的第一个元素所在位置
console.log(index) // 2index = arr.lastIndexOf("d") //返回反序查找的第一个元素所在位置
console.log(index) // 3// 对象
let persons = [{ id: 1, name: '张三', age: 23 },{ id: 2, name: '李四', age: 11 },{ id: 3, name: '王五', age: 16 }
];// persons.forEach((value, index, array) => {
//     console.log(value, index)
// })// find() 方法返回相应的对象, 从未返回真值，则 find() 方法返回 undefined
const person = persons.find(obj => {return obj.id === 2;
})console.log(person); // {  "id": 2,  "name": "李四",  "age": 11} // filter, 也可以反向选择
const p1 = persons.filter(obj => {// return obj.name != "李四"return obj.id == 2;
})console.log(p1); // {  "id": 2,  "name": "李四",  "age": 11} const p2 = persons.filter(obj => {return obj.id != 2;
})console.log(p2); 
/**
[{"id": 1,"name": "张三","age": 23
}, {"id": 3,"name": "王五","age": 16
}]*/// 查找元素的index
const c1 = persons.findIndex(person => {return person.name == "李四"
})console.log(c1); // 1
console.log(persons[c1]) //{  "id": 2,  "name": "李四",  "age": 11} 

七、连接数组元素

let arr: Array<string> = ["a", "b", "c", "d"]let joinString = arr.join(",") //返回查找到的第一个元素所在位置
console.log(joinString) // "a,b,c,d" joinString = arr.join("-") //返回反序查找的第一个元素所在位置
console.log(joinString) // "a-b-c-d" 

八、排序、反序数组

let arr: Array<number> = [1,4,3,5,2]arr.sort()
console.log(arr) // [1, 2, 3, 4, 5] arr.reverse() //返回反序查找的第一个元素所在位置
console.log(arr) // [5, 4, 3, 2, 1] 

九、遍历数组，对象

• 定义数组

let persons = [{ id: 1, name: '张三', age: 23 },{ id: 2, name: '李四', age: 11 },{ id: 3, name: '王五', age: 16 }
];

1. for 循环

for ( let index = 0; index < persons.length; ++index) {console.log(persons[index]);
}

2. for…in 循环

for (let index in persons) {console.log(persons[index])  
}

3. for…of循环

for (let person of persons) {console.log(person)  
}

4. forEach循环

persons.forEach((value, index, array) => {console.log(value, index)
})