Hướng dẫn can you use and in an if statement javascript? - bạn có thể sử dụng và trong một câu lệnh if javascript không?

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Trong bài viết này, tôi sẽ giải thích tuyên bố

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

Nếu ... tuyên bố khác trong JavaScript là gì?

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

Các giá trị

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

if [condition is true] {
   // code is executed
} else {
   // code is executed
}

Bất kỳ giá trị nào không được định nghĩa là

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

Dưới đây là danh sách & nbsp; ____ ____ 20 giá trị:

• false
• 0 [không]
• -0 [không âm]
• 0n [Bigint Zero]

• if [condition 1 is true] {
     // code is executed
  } else if [condition 2 is true] {
    // code is executed
  } else {
     // code is executed
  }

  0,

  if [condition 1 is true] {
     // code is executed
  } else if [condition 2 is true] {
    // code is executed
  } else {
     // code is executed
  }

  1,

  if [condition 1 is true] {
     // code is executed
  } else if [condition 2 is true] {
    // code is executed
  } else {
     // code is executed
  }

  2 [Chuỗi trống]
• null
• chưa xác định
• Nan [không phải là một số]

Ví dụ về nếu ... câu lệnh khác trong JavaScript

Trong ví dụ này, điều kiện cho câu lệnh

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

if [condition 1 is true] {
   // code is executed
} else if [condition 2 is true] {
  // code is executed
} else {
   // code is executed
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

But if I change the

if [condition 1 is true] {
   // code is executed
} else if [condition 2 is true] {
  // code is executed
} else {
   // code is executed
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

Examples of multiple conditions [if...else if...else statements] in JavaScript

Sẽ có những lúc bạn muốn kiểm tra nhiều điều kiện. Đó là nơi khối

if [condition 1 is true] {
   // code is executed
} else if [condition 2 is true] {
  // code is executed
} else {
   // code is executed
}

if [condition 1 is true] {
   // code is executed
} else if [condition 2 is true] {
  // code is executed
} else {
   // code is executed
}

Khi câu lệnh

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

if [condition 1 is true] {
   // code is executed
} else if [condition 2 is true] {
  // code is executed
} else {
   // code is executed
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

Trong ví dụ này, khối

if [condition 1 is true] {
   // code is executed
} else if [condition 2 is true] {
  // code is executed
} else {
   // code is executed
}

const age = 18;

if [age < 18] {
  console.log["Alice is under 18 years old."];
} else if [age >= 18 && age = 18 && age = 18 && age = 18 && age = 18 && age = 18 && age = 18 && age = 18 && age = 18 && age = 18 && age = 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

Trong ví dụ này, vì tuổi lớn hơn 16 và biến

const pet = "dog";

if [pet === "lizard"] {
  console.log["I own a lizard"];
} else if [pet === "dog"] {
  console.log["I own a dog"];
} else if [pet === "cat"] {
  console.log["I own a cat"];
} else if [pet === "snake"] {
  console.log["I own a snake"];
} else if [pet === "parrot"] {
  console.log["I own a parrot"];
} else {
  console.log["I don't own a pet"];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 17;
const ownsCar = true;

if [age >= 16 && ownsCar] {
  console.log["Jerry is old enough to drive and has his own car."];
} else {
  console.log["Jerry does not drive."];
}

if [condition 1 is true] {
   // code is executed
} else if [condition 2 is true] {
  // code is executed
} else {
   // code is executed
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

If I change the

if [condition 1 is true] {
   // code is executed
} else if [condition 2 is true] {
  // code is executed
} else {
   // code is executed
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 13;
const ownsCar = true;

if [age >= 16 && ownsCar] {
  console.log["Jerry is old enough to drive and has his own car."];
} else {
  console.log["Jerry does not drive."];
}

The logical OR [||] operator and if...else statements in JavaScript

Trong toán tử logic hoặc [

const pet = "dog";
 
switch [pet] {
  case "lizard":
    console.log["I own a lizard"];
    break;
  case "dog":
    console.log["I own a dog"];
    break;
  case "cat":
    console.log["I own a cat"];
    break;
  case "snake":
    console.log["I own a snake"];
    break;
  case "parrot":
    console.log["I own a parrot"];
    break;
  default:
    console.log["I don't own a pet"];
    break;
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

Trong ví dụ này, mặc dù biến

const pet = "dog";
 
switch [pet] {
  case "lizard":
    console.log["I own a lizard"];
    break;
  case "dog":
    console.log["I own a dog"];
    break;
  case "cat":
    console.log["I own a cat"];
    break;
  case "snake":
    console.log["I own a snake"];
    break;
  case "parrot":
    console.log["I own a parrot"];
    break;
  default:
    console.log["I don't own a pet"];
    break;
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 17;
const ownsCar = true;

if [age >= 16 && ownsCar] {
  console.log["Jerry is old enough to drive and has his own car."];
} else {
  console.log["Jerry does not drive."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const boyfriendIsPaying = true;
const isSale = false;

if [boyfriendIsPaying || isSale] {
  console.log["Jesse will go shopping."];
} else {
  console.log["Jesse will not go shopping."];
}

const age = 17;
const ownsCar = true;

if [age >= 16 && ownsCar] {
  console.log["Jerry is old enough to drive and has his own car."];
} else {
  console.log["Jerry does not drive."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

If I were to change the value of the

const age = 17;
const ownsCar = true;

if [age >= 16 && ownsCar] {
  console.log["Jerry is old enough to drive and has his own car."];
} else {
  console.log["Jerry does not drive."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

The logical NOT [!] operator and if...else statements in JavaScript

Toán tử không [

const age = 17;
const ownsCar = true;

if [age >= 16 && ownsCar] {
  console.log["Jerry is old enough to drive and has his own car."];
} else {
  console.log["Jerry does not drive."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

Chúng tôi có thể sửa đổi ví dụ từ trước đó để sử dụng toán tử

const age = 17;
const ownsCar = true;

if [age >= 16 && ownsCar] {
  console.log["Jerry is old enough to drive and has his own car."];
} else {
  console.log["Jerry does not drive."];
}

const age = 17;
const ownsCar = true;

if [age >= 16 && ownsCar] {
  console.log["Jerry is old enough to drive and has his own car."];
} else {
  console.log["Jerry does not drive."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

Conditional [ternary] operator in JavaScript

Nếu bạn có một câu lệnh

const age = 18;

if [age < 18] {
  console.log["Alice is under 18 years old."];
} else if [age >= 18 && age = 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

Điều kiện đi trước dấu

const age = 13;
const ownsCar = true;

if [age >= 16 && ownsCar] {
  console.log["Jerry is old enough to drive and has his own car."];
} else {
  console.log["Jerry does not drive."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 13;
const ownsCar = true;

if [age >= 16 && ownsCar] {
  console.log["Jerry is old enough to drive and has his own car."];
} else {
  console.log["Jerry does not drive."];
}

const boyfriendIsPaying = true;
const isSale = false;

if [boyfriendIsPaying || isSale] {
  console.log["Jesse will go shopping."];
} else {
  console.log["Jesse will not go shopping."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

Trong ví dụ này, vì tuổi lớn hơn 18, thì thông điệp đến giao diện điều khiển sẽ là "có thể bỏ phiếu".

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 18;

if [age < 18] {
  console.log["Alice is under 18 years old."];
} else if [age >= 18 && age = 18 && age = 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

Sự kết luận

Các câu lệnh

const age = 18;

if [age < 18] {
  console.log["Alice is under 18 years old."];
} else if [age >= 18 && age = 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

const age = 12;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

Sẽ có những lúc bạn muốn kiểm tra nhiều điều kiện và bạn có thể sử dụng câu lệnh

const age = 18;

if [age >= 18] {
  console.log["Nick is an adult."];
} else {
  console.log["Nick is a child."];
}

Nếu bạn cảm thấy như câu lệnh

const age = 18;

if [age < 18] {
  console.log["Alice is under 18 years old."];
} else if [age >= 18 && age = 18 && age = 18 && age = 18 && age