JavaScript Return Command

This article gives an overview of the return statement in JavaScript. The return statement is placed after the execution of a function and is used to stop any further processing within that function while returning a specified value. In JavaScript, it is necessary for a function to explicitly include a return statement to convey the value of the expression contained within it. Further, when the return statement is not specified in the code, the compiler or interpreter automatically sends back a value from the function. The common case for this returned value by the function is it goes back to the one that invoked it.

Functions can return values in two forms:

• Primitive values (such as number, number, Boolean, etc.)
• Object types (such as array, objects, functions, etc.)

Syntax

In this context, (expression) is:

• Optional
• It is the value the function is going to send back
• In case an expression in the return statement is left empty, then this function returns undefined.

Automatic Semicolon Insertion (ASI)

This would follow the rule of Automatic Semicolon Insertion, or ASI. This implies that no line terminator is present between the return statement and the corresponding expression to which it may refer. But if the return statement is declared in this way:

If the return statement is expressed in the following manner:

It can be reformulated by Automatic Semicolon Insertion (ASI) as:

This will print a warning that indicates that there is an unreachable code after the return statement.

With this, to solve the problem and avoid ASI, the expression that follows the return must be in the parentheses:

Functionality of the return statement in JavaScript with illustrations

This article will explore how return works in JavaScript. A return statement is mostly used inside a function to provide a value while ending the execution of that function. By default, an expression that doesn't evaluate to a value returns undefined.

Here is a simple example of how a return statement is used in JavaScript:

Example: Define a function that computes and returns the area of the triangle.

Code

Output

Example 1

Below, we will examine a straightforward illustration of a return statement in JavaScript.

Code

Output

In the program mentioned above, there is a function named "myFunction" that takes in two arguments and returns their sum. This function is defined so that it will accept any numerical pair of input values, thus returning the result of their sum. The return statement includes the expression "a1 + a2," which performs the addition. Furthermore, the result from this computation is assigned to a variable called "result" using the assignment operator ("="). The value of the expression is then stored in the variable, which is then printed out every time the function is called.

Next we will look at an example of what occurs should we remove the return statement altogether. In this case, we need to be sure that we explicitly return the result of the expression; otherwise, the interpreter will just print out an undefined output from the function.

Example 2

Code

Output

In the function shown above, there is no return statement during the computation of a number's square times its product since the declared function is template. It thus means that no return keyword would be placed before the expression and the value of that expression will therefore be printed "undefined". Consequently, the square of a number will print out "undefined" instead of giving the correct square value of that number.

This paper had explained the use of the return statement in JavaScript as follows:

Here is an example of a function that demonstrates the use of return to get out of the loop.

Example 3

Code

Output

Above, the function "example" is defined that has a for loop and it is anticipated to print some values. Still, the return statement in the function will end the loop at the finding of the value of 5 though the loop can run up to 10.

Conclusion

In the section above, it is shown that the return statement in JavaScript has several different functions.

1. We reviewed how the return statement causes execution to terminate at a defined function in the program. That is, at the return statement, the execution would stop and pass the value obtained from the function call that includes an argument or code whose expected result should give a value.
2. We talked about what happens when we forget to use the return keyword in a function and try to return a value; in such cases, the function will return undefined.
3. Automatic Semicolon Insertion (ASI) affects the return statement by suggesting that no line terminator should be placed between the return keyword and the expression.