常用知识点
数据类型
boolean, number, string, bigint, symbol, any, null, undefined, array, tuple, object
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62let age: number = 25;
const age = 25;
let scores: number[] = [12, 13];
let entry: [string, number] = ["1", 2];
// return type can be void
function sum(a:number=5, b?: number): number {
console.log(`ID: ${a}`);
return a + b;
}
interface User {
id: string;
age?: number;
readonly name: string;
}
type ID = string | number;
let userId: ID = "ab";
type Status = "pending" | "active";
enum Color {
Red = "Red",
Green = "Green"
}
// 类型推断: 函数变量需要写类型，函数内大部分不需要写
const map = new Map<string, number>([
["key1", "value1"], // like tuple
["key2", "value2"]
]);
map.set("a", 9);
map.forEach((v, k) => {console.log(`${k}:${v}`)}); // recommend
for(const [k, v] of map){
if(typeof v == 'string')
console.log(`${k}:${v}`);
}
// class: readonly, private, protected, public, constructor
// class Dob extends Animal
for (let i=0; i < 5; i++) {
let b = i + 1;
}
const nums = [1, 2, 3];
nums.forEach((num) => {let t = num + 1;}); // recommend
// 剩余函数
function sum2(...nums: number[]){
let s = 0;
nums.forEach(num => {s += num;});
for (const num of nums) {
s += num;
}
return s;
}
let bb = sum2(2, 3, 4);
// 匿名函数
const add = (a: number, b:number) => {
return a + b;
}
| 类型 | 函数名 | 作用 | 输入参数 | 返回值 | 例子 |
|---|---|---|---|---|---|
| for | range | 和len结合使用相当于取某范围List下标,第三个参数为步长 | N/A | N/A | **for i in range(len(nums))**前闭后开,用逗号 |
| map | get | ||||
| map | set | ||||
| map | has | ||||
| map | size | ||||
| map | delete | ||||
| map | clear | ||||
| map | keys | ||||
| map | values | ||||
| map | entries | ||||
| string | join | 跟python相反 | nums.join(""); |
