js中冒号什么作用

const person = {
  name: "Alice",
  age: 25,
  occupation: "Engineer"
};

switch (day) {
  case 1:
    console.log("Monday");
    break;
  case 2:
    console.log("Tuesday");
    break;
  default:
    console.log("Other day");
}

outerLoop: for (let i = 0; i < 3; i++) {
  innerLoop: for (let j = 0; j < 3; j++) {
    if (i === 1 && j === 1) {
      break outerLoop;
    }
    console.log(`i: ${i}, j: ${j}`);
  }
}

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

class Person {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }

  greet() {
    console.log(`Hello, my name is ${this.name}`);
  }
}

let name: string = "Alice";
let age: number = 25;

const isAdult = age >= 18 ? "Adult" : "Minor";

let isAvailable: boolean = true;