Default Javascript Settings

Michael Zippo 04.11.2021

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The default settings make it much easier to work with functions. Using the default settings, you can tell your functions which settings to use in case you haven’t specified. This helps avoid errors and makes the code more readable.

JavaScript introduces default settings in ES2015. These allow you to initialize a function with default values.

In this guide, we’ll talk about what the default settings are, how you can use them, and what types of expressions you can specify as the default setting. We’re going to go through a few examples so that you have all the code you need to get started.

Parameters vs. arguments: the battle

Before we begin, let’s answer an age-old question from beginners: what is the difference between a parameter and an argument? You should know the difference before you start working with presets in JavaScript.

A parameter is a named variable that you pass to a JavaScript function. A parameter is never assigned a direct value. There is a placeholder for a value that you will pass to a function. Here is an example parameter:

In this example, "name" is our parameter. It has no value assigned.

Arguments, on the other hand, are values ‚Äã‚Äãthat are passed to a function:.

Our code returns: "Hello, Brett". "Brett" is an example of an argument, which was the value we were passing through our function

Calling a function without specifying all of its parameters can lead to an error:

Our code returns: Hello, undefined . Indeed, we did not adopt a value to our function

parameters by JavaScript default

We can overcome this problem by specifying a default default parameter. System allows you to specify a value that will be assigned to a parameter if none is specified.

Default value assignment uses assignment operator:

Our code returns: Hello, World. As you can see, we haven’t specified an argument in this example. Instead of this, we have set a default function parameter. In this case, whenever an argument is not specified, the value of the "name" parameter in our function becomes "World".

This is much easier than having to manually check if av alue is specified.

A default parameter can have a primitive or object assigned as a value. Here are some examples of valid default parameters:

There is no limit to the number of default parameters you can specify in a function. Consider the following code:

Our code returns:

In this example, we’ve specified two default settings: coffee and price. You can also mix the settings you specify between the default and normal settings. When you do this, you need to put all the regular settings before the default settings. Consider this example:

Our code returns:

We have specified a subject: Cappuccino. This is the name of the coffee we ordered. Since we have not specified a default value for this parameter, we must specify an argument value; otherwise "undefined" would be returned

us stated that the default for "price" should be "1.75". Since we set this to default, whenever we don’t specify a price, it will automatically be set to "1.75‚".

It is important to specify the regular settings before the default settings. Indeed, the values ‚Äã‚Äãof the parameters are regularly assigned in the order of appearance in the function call.

Functions as Default Parameter

You can set a function as default parameter, useful if the value you want to pass to a function is calculated using another function.

In the following code snippet, we’ll create a function that generates a pseudo-random username for a new video game player:

Our code returns:

pause Let our code

We have declared a function called getRandomUsername () which generates a pseudo-random username. It works by generating a random number and the selection at random a name of user starting from a list of four names of user. The random number is then appended to the end of the username. This function returns the newly generated username

In our createUser, we have set the default " username" parameter equal to our getRandomUsername ( ) . This means that whenever we do not specify a username for our new user, a random one is generated.

Our code then prints out the user ’s username and email address . At the Consol.

Conclusion

I default settings allow you to define a value that will be assigned to a parameter, if one is not specified as an argument in a function call. parameters help make your functions easier to read and reduce problems that can arise when a value is not passed to a function.

You are now ready to start working with JavaScript default settings like an expert!

We hope this article has helped you to resolve the problem. Apart from Default Javascript Settings, check other code Python module-related topics.