How to use return statement in JavaScript

How to use return in JavaScript requires specific code examples

In JavaScript, return is a very important keyword, it is usually used to return values ​​in functions or end the execution of the function. The return statement is used to return a value to the caller of the function and terminate the execution of the function.

The return statement can be used anywhere in a function and can return any JavaScript data type, including numbers, strings, booleans, objects, etc. When the return statement in a function is executed, the function immediately stops execution and returns the specified value. The following are some specific usage methods and sample codes about return:

1. Return numeric value:

function calculateSum(a, b) {
  return a + b;
}

let sum = calculateSum(5, 3);
console.log(sum); // 输出 8

The above code defines a function calculateSum, It takes two parameters a and b and returns their sum. When calling the function, the returned value is assigned to the variable sum, and the result is printed through console.log.

2. Return string value:

function generateMessage(name) {
  return "Hello, " + name + "! Welcome to our website.";
}

let message = generateMessage("John");
console.log(message); // 输出 "Hello, John! Welcome to our website."

In this example, the function generateMessage accepts a parameter name, and in the character Returns a string with a welcome message. After calling the function, the returned value is assigned to the variable message and output through console.log.

3. Returns a Boolean value:

function isEven(number) {
  if (number % 2 === 0) {
    return true;
  } else {
    return false;
  }
}

let result = isEven(6);
console.log(result); // 输出 true

In the above example, the function isEven accepts a parameter number and determines whether is an even number. If it is an even number, return true, otherwise return false. By calling the function, assign the result to the result variable and output it.

4. Return object:

function createPerson(name, age, gender) {
  return {
    name: name,
    age: age,
    gender: gender
  };
}

let person = createPerson("Alice", 25, "female");
console.log(person); // 输出 { name: 'Alice', age: 25, gender: 'female' }

In this example, the function createPerson accepts three parameters and is used to create an object containing name, age and gender. properties object. By calling the function, assign the returned object to person and then output it.

5. End the execution of the function early:

function checkInput(value) {
  if (value === "") {
    return;
  }

  // 执行其他逻辑
  console.log("Input value is not empty!");
}

checkInput(""); // 没有输出
checkInput("Hello"); // 输出 "Input value is not empty!"

In this example, if the value of value is an empty string, it will be returned directly. Subsequent logic will be executed. You can see the difference in output results by passing in different parameters of empty strings and non-empty strings when calling the function.

Through the above examples, we can see how to use the return statement and its importance in JavaScript functions. It returns a value to the caller of the function and terminates the function execution when appropriate. Combined with function parameters and logical processing, we can write more flexible and powerful JavaScript functions.

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