What are the basic rules for JavaScript parameters?
In this tutorial, let’s discuss the basic rules of JavaScript parameters.
JavaScript functions are codes that perform specific tasks. Function arguments are a list of names from the function definition. Parameters are also called formal parameters or formal parameters.
We can declare parameters according to the following syntax.
grammar
function functionName(param1, param2) { }
When a parameter has no value, the default value will be used.
rule
Declare default parameters as final parameters to avoid errors.
JavaScript function definition does not specify parameter types.
JavaScript functions do not check the type of input parameters.
JavaScript functions do not check the number of input parameters.
Example 1
is:Example 1
The following program declares the default parameters of a function. Therefore, when there are no parameter values, the function assumes the default value.
<html> <body> <h2 id="Default-parameters-in-JavaScript">Default parameters in JavaScript </h2> <p> <b> Input = Sum(10) </b> </p> <p> <b> Input = Sum(10,30) </b> </p> <div id="paramDefBtnWrap"> <button id="paramDefBtn"> Run </button> </div> <p id="paramDefOut"> </p> <script> var paramDefOut = document.getElementById("paramDefOut"); var paramDefBtnWrap = document.getElementById("paramDefBtnWrap"); var paramDefBtn = document.getElementById("paramDefBtn"); var paramDefInpStr = ""; paramDefBtn.onclick = function() { //paramDefBtnWrap.style.display = "none"; function sum(param1, param2 = 20) { var sum = param1 + param2; paramDefInpStr += param1 + " + " + param2 + " = " + sum + "<br><br>"; } sum(10); sum(10, 30); paramDefOut.innerHTML = paramDefInpStr; }; </script> </body> </html>
Example 2
is:Example 2
The following program accepts an integer parameter and a string parameter input. The output returns 'NaN' because the function did not check the parameter types.
<html> <body> <h2 id="Illustrating-parameter-type-and-argument-type"> Illustrating parameter type and argument type</h2> <p> <b> Input = Multiply(10, 'ten') </b> </p> <div id="paramArgBtnWrap"> <button id="paramArgBtn"> Run </button> </div> <p id="paramArgOut"> </p> <script> var paramArgOut = document.getElementById("paramArgOut"); var paramArgBtnWrap = document.getElementById("paramArgBtnWrap"); var paramArgBtn = document.getElementById("paramArgBtn"); var paramArgInpStr = ""; paramArgBtn.onclick = function() { //paramArgBtnWrap.style.display = "none"; function mult(param1, param2) { var prod = param1 * param2; paramArgInpStr += "Argument 1 type is " + typeof(param1) + "<br><br>"; paramArgInpStr += "Argument 2 type is " + typeof(param2) + "<br><br>"; paramArgInpStr += param1 + " × " + param2 + " = " + prod + "<br><br>"; } mult(10, 'ten'); paramArgOut.innerHTML = paramArgInpStr; }; </script> </body> </html>
Example 3
is:Example 3
The following program has three parameters and four parameters. The length property of ‘arguments’ objects and functions differentiates them for us.
<html> <body> <h2 id="Illustrating-number-of-arguments-and-parameters-in-a-function"> Illustrating number of arguments and parameters in a function</h2> <p> <b> Input = 1, 'one', Date, {} </b> </p> <div id="infArgBtnWrap"> <button id="infArgBtn"> Run </button> </div> <p id="infArgOut"> </p> <script> var infArgOut = document.getElementById("infArgOut"); var infArgBtnWrap = document.getElementById("infArgBtnWrap"); var infArgBtn = document.getElementById("infArgBtn"); var infArgInpStr = ""; infArgBtn.onclick = function() { //infArgBtnWrap.style.display = "none"; function argFunction(arg1, arg2, arg3) { infArgInpStr += "Function Parameters = " + argFunction.length + '<br><br>'; infArgInpStr += "Function Arguments = " + arguments.length + '<br><br>'; infArgInpStr += "Arguments are, <br><br>" for (i = 0; i < arguments.length; i++) { infArgInpStr += argFunction.arguments[i] + "<br>"; } infArgOut.innerHTML = infArgInpStr; } argFunction(1, 'one', Date, {}); }; </script> </body> </html>
This tutorial teaches us the basic parameter rules. Be sure to declare a default parameter value to avoid errors. Pay attention to parameter types and parameter value types when coding. Be careful to follow the parameter order.
The above is the detailed content of What are the basic rules for JavaScript parameters?. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

Frequently Asked Questions and Solutions for Front-end Thermal Paper Ticket Printing In Front-end Development, Ticket Printing is a common requirement. However, many developers are implementing...

There is no absolute salary for Python and JavaScript developers, depending on skills and industry needs. 1. Python may be paid more in data science and machine learning. 2. JavaScript has great demand in front-end and full-stack development, and its salary is also considerable. 3. Influencing factors include experience, geographical location, company size and specific skills.

JavaScript is the cornerstone of modern web development, and its main functions include event-driven programming, dynamic content generation and asynchronous programming. 1) Event-driven programming allows web pages to change dynamically according to user operations. 2) Dynamic content generation allows page content to be adjusted according to conditions. 3) Asynchronous programming ensures that the user interface is not blocked. JavaScript is widely used in web interaction, single-page application and server-side development, greatly improving the flexibility of user experience and cross-platform development.

How to merge array elements with the same ID into one object in JavaScript? When processing data, we often encounter the need to have the same ID...

Learning JavaScript is not difficult, but it is challenging. 1) Understand basic concepts such as variables, data types, functions, etc. 2) Master asynchronous programming and implement it through event loops. 3) Use DOM operations and Promise to handle asynchronous requests. 4) Avoid common mistakes and use debugging techniques. 5) Optimize performance and follow best practices.

Discussion on the realization of parallax scrolling and element animation effects in this article will explore how to achieve similar to Shiseido official website (https://www.shiseido.co.jp/sb/wonderland/)...

Explore the implementation of panel drag and drop adjustment function similar to VSCode in the front-end. In front-end development, how to implement VSCode similar to VSCode...

In-depth discussion of the root causes of the difference in console.log output. This article will analyze the differences in the output results of console.log function in a piece of code and explain the reasons behind it. �...
