TypeScript数组和对象的操作

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>=newArray<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>=newArray<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 =7

arr = 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)// 2

index = 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 undefinedconst 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indexconst c1 = persons.findIndex(person =>{return person.name =="李四"})console.log(c1);// 1console.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]);}

1. for…in 循环

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

1. for…of循环

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

1. forEach循环

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