What happens when JavaScript passes a value without double quotes?

JavaScript is a dynamic, weakly typed programming language mainly used to create interactive web pages and applications. It uses some common programming concepts, including variables, functions, and data types, and also supports numerous JavaScript libraries and frameworks, allowing developers to write code more efficiently.

In JavaScript, passing by value means passing a value from one variable to another. Typically, you pass a string, number, or Boolean value to another variable. When passing a string, you usually need to use quotation marks to enclose the text so that it can be passed correctly. For example:

var str = "Hello world!";
var newStr = str;

In the above code, assign the "Hello world!" string to the variable str, and then This string is passed to the variable newStr. Since the string needs to be enclosed in quotes, we use double quotes.

However, sometimes you may encounter situations where quotes are not required when passing values ​​in JavaScript. For example, in some cases you may need to pass the value of a variable instead of a string, in which case quotes are not required.

For example, suppose we have a function that adds two numbers and returns the result:

function addNum(num1, num2){
    return num1 + num2;
}

var num1 = 10;
var num2 = 5;
var total = addNum(num1, num2);
console.log(total);

In the above code, we define an addNum function that adds num1 Add two numbers with num2 and return the result. We also define two variables num1 and num2 and set their values ​​to 10 and 5 respectively. We then call the addNum function to pass these two numbers to the function and save the return value of the function into the variable total. Finally, we use console.log() to output the value of total.

In this example, we are passing no value using quotes. We passed the two variables num1 and num2 because they have been assigned as numbers, not strings.

In addition, in JavaScript, numbers and Boolean values ​​do not need to be enclosed in quotes. For example, we can pass a Boolean value like this:

var isTrue = true;
var isFalse = false;
var newBool1 = isTrue;
var newBool2 = isFalse;

In this example, we assign the Boolean values ​​true and false to the variables isTrue and isFalse respectively. Then, we pass these two variables to two other variables, newBool1 and newBool2, without using quotes.

In general, whether JavaScript needs to use quotes when passing values ​​depends on the data type of the value being passed. When passing a string, you need to use quotes, but when passing a number, Boolean value, or variable, you don't need to use quotes. This is because JavaScript has strict data type definitions, and passing different types of values ​​requires different methods to ensure that the code can run correctly.

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