Boolean() The constructor can be used to create Boolean objects as well as Boolean primitives, representing true or false values .
In the code below, I detail the creation of Boolean values in JavaScript.
Example: sample52.html
<!DOCTYPE html><html lang="en"><body><script> // Create a Boolean object using the new keyword and the Boolean() constructor. var myBoolean1 = new Boolean(false); // Using new keyword. console.log(typeof myBoolean1); // Logs 'object'. // Create a Boolean literal/primitive by directly using the number constructor without new. var myBoolean2 = Boolean(0); // Without new keyword. console.log(typeof myBoolean2); // Logs 'boolean'. // Create Boolean literal/primitive (constructor leveraged behind the scenes). var myBoolean3 = false; console.log(typeof myBoolean3); // Logs 'boolean'. console.log(myBoolean1, myBoolean2, myBoolean3); // Logs false false false. </script></body></html>
Boolean() Parameters
Boolean() The constructor converts an argument to a Boolean value (i.e. true or false). Any valid JavaScript value that is not 0, -0, null, false, NaN, undefined, or the empty string ("") will be converted to true. In the following example, we create two Boolean object values: a true and a false.
Example: sample53.html
<!DOCTYPE html><html lang="en"><body><script> // Parameter passed to Boolean() = 0 = false, thus foo = false var foo = new Boolean(0) console.log(foo); // Parameter passed to Boolean() = Math = true, thus bar = true var bar = new Boolean(Math) console.log(bar); </script></body></html>
When used with the new keyword, an instance from the Boolean() constructor produces an actual complex object. You should avoid using the Boolean() constructor to create boolean values (instead use literals/raw numbers) because of potential issues related to the typeof operator. The typeof operator reports Boolean objects as "object" instead of the original label ("boolean") as you might expect. Additionally, literal/raw values are written faster.
Boolean() Properties and methods
Boolean() The object has the following properties:
Properties (for example, Boolean.prototype;):
prototype
Boolean object instance properties and methods
Boolean object instances have the following properties and methods (excluding inherited properties and methods):
Instance properties (e.g., var myBoolean = false; myBoolean.constructor;):
Constructor
Instance methods (e.g., var myNumber = false; myBoolean.toString();):
toSource()toString()valueOf()
Non-original False Boolean objects are converted to True
A false Boolean object created from the Boolean() constructor (rather than a primitive value) is an object, and the object is converted to true. Therefore, when a false Boolean object is created via the Boolean() constructor, the value itself is converted to true. In the example below, I demonstrate how a false Boolean object is always "true".
Example: sample54.html
<!DOCTYPE html><html lang="en"><body><script>
var falseValue = new Boolean(false);
console.log(falseValue); // We have a false Boolean object, but objects are truthy.
if (falseValue) { // Boolean objects, even false Boolean objects, are truthy.
console.log('falseValue is truthy');
}
</script></body></html>
If you need to convert a non-Boolean value to a Boolean value, just use the Boolean() constructor without the new keyword, and the returned value will be the original value instead Not a Boolean object. p>
Some things are false, everything else is true
Already mentioned, but worth mentioning again as it relates to conversions: if value is 0, -0, null, false, NaN, undefined, or an empty string ("") is false. If used in a Boolean context, any value in JavaScript other than the above will be converted to true (i.e. if (true) {};).
Example: sample55.html
<!DOCTYPE html><html lang="en"><body><script>
// All of these return a false Boolean value.
console.log(Boolean(0));
console.log(Boolean(-0));
console.log(Boolean(null));
console.log(Boolean(false));
console.log(Boolean(''));
console.log(Boolean(undefined));
console.log(Boolean(null));
// All of these return a true Boolean value.
console.log(Boolean(1789));
console.log(Boolean('false')); // 'false' as a string is not false the Boolean value.
console.log(Boolean(Math));
console.log(Boolean(Array()));
</script></body></html>
in conclusion
It's critical to know which JavaScript values are simplified to false so that you know that all other values are treated as true.
The above is the detailed content of How to determine whether it is a Boolean value. For more information, please follow other related articles on the PHP Chinese website!
How to add a comment box to WordPressApr 20, 2025 pm 12:15 PMEnable comments on your WordPress website to provide visitors with a platform to participate in discussions and share feedback. To do this, follow these steps: Enable Comments: In the dashboard, navigate to Settings > Discussions, and select the Allow Comments check box. Create a comment form: In the editor, click Add Block and search for the Comments block to add it to the content. Custom Comment Form: Customize comment blocks by setting titles, labels, placeholders, and button text. Save changes: Click Update to save the comment box and add it to the page or article.
How to copy sub-sites from wordpressApr 20, 2025 pm 12:12 PMHow to copy WordPress subsites? Steps: Create a sub-site in the main site. Cloning the sub-site in the main site. Import the clone into the target location. Update the domain name (optional). Separate plugins and themes.
How to write a header of a wordpressApr 20, 2025 pm 12:09 PMThe steps to create a custom header in WordPress are as follows: Edit the theme file "header.php". Add your website name and description. Create a navigation menu. Add a search bar. Save changes and view your custom header.
How to display wordpress commentsApr 20, 2025 pm 12:06 PMEnable comments in WordPress website: 1. Log in to the admin panel, go to "Settings" - "Discussions", and check "Allow comments"; 2. Select a location to display comments; 3. Customize comments; 4. Manage comments, approve, reject or delete; 5. Use <?php comments_template(); ?> tags to display comments; 6. Enable nested comments; 7. Adjust comment shape; 8. Use plugins and verification codes to prevent spam comments; 9. Encourage users to use Gravatar avatar; 10. Create comments to refer to
How to upload source code for wordpressApr 20, 2025 pm 12:03 PMYou can install the FTP plug-in through WordPress, configure the FTP connection, and then upload the source code using the file manager. The steps include: installing the FTP plug-in, configuring the connection, browsing the upload location, uploading files, and checking that the upload is successful.
How to copy wordpress codeApr 20, 2025 pm 12:00 PMHow to copy WordPress code? Copy from the admin interface: Log in to the WordPress website, navigate to the destination, select the code and press Ctrl C (Windows)/Command C (Mac) to copy the code. Copy from a file: Connect to the server using SSH or FTP, navigate to the theme or plug-in file, select the code and press Ctrl C (Windows)/Command C (Mac) to copy the code.
What to do if there is an error in wordpressApr 20, 2025 am 11:57 AMWordPress Error Resolution Guide: 500 Internal Server Error: Disable the plug-in or check the server error log. 404 Page not found: Check permalink and make sure the page link is correct. White Screen of Death: Increase the server PHP memory limit. Database connection error: Check the database server status and WordPress configuration. Other tips: enable debug mode, check error logs, and seek support. Prevent errors: regularly update WordPress, install only necessary plugins, regularly back up your website, and optimize website performance.
How to close comments with wordpressApr 20, 2025 am 11:54 AMHow to turn off a comment in WordPress? Specific article or page: Uncheck Allow comments under Discussion in the editor. Whole website: Uncheck "Allow comments" in "Settings" -> "Discussion". Using plug-ins: Install plug-ins such as Disable Comments to disable comments. Edit the topic file: Remove the comment form by editing the comments.php file. Custom code: Use the add_filter() function to disable comments.
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
Dreamweaver Mac version
Visual web development tools
ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment
SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.
DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software
