JavaScript Try..Catch


JavaScript Errors - Try and Catch

The try...catch statement is representing a block of statements. The block is used to try expressions, and specify a response if an exception is thrown.

The try statement is testing a code block for errors.

The catch statement is where you take care of and handle the error.

The throw statement is where you can create custom errors.

The finally statement executes code after try and catch. This is done regardless of the result.

JS JavaScript - JavaScript Errors - Invalid or unexpected token

try {
    eval('alert("Hello bumblebee)');
}
catch(error) {
    alert(error);
    // Result: SyntaxError: Invalid or unexpected token
}

Learn more about JavaScript Errors

Some exception messages might vary depending on the browser being used.


JavaScript - Finally

The finally statement can be used for closing a resource.

JS JavaScript - Try..Catch - Finally

openTheFileReader();
 
try {
// Write the file to disk.
    writeFileToDisk(data);
}
finally {
    closeTheFileReader(); 
    // Close the resource
}

Learn more about JavaScript Debugging Learn more about JavaScript Developer Tools

Error Name Values

There are six different values that can be returned by the name property for an error.


EvalError That creates an instance that represents an error that occurs regarding the global function eval().

InternalError That creates an instance that represents an error that occurs when an internal error in the JavaScript engine is thrown.

RangeError That creates an instance that represents an error that occurs when a numeric variable or parameter is outside of its valid range.

ReferenceError That creates an instance that represents an error that occurs when de-referencing an invalid reference.

SyntaxError That creates an instance that represents a syntax error that occurs while parsing code in eval().

TypeError That creates an instance that represents an error that occurs when a variable or parameter is not of a valid type.

URIError That creates an instance that represents an error that occurs when encodeURI() or decodeURI() are passed invalid parameters.



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JS JavaScript: Events

Events are actions or occurrences that happen to HTML elements.

JavaScript can act when an HTML Event occurs.

Events can represent everything from basic user interactions to automated notifications of things happening in the rendering model.

JS JavaScript: Var

Var is a keyword that is used to declare a variable.

But, you should NOT use var, use let when declaring a variable.

One of the most important things is that you should try to keep things simple!

JS JavaScript: Comments

JavaScript comments can be used to to explain and make the code more readable. JavaScript comments can also prevent execution of code.

It is possible to comment code as a single-line comment or as a multi-line comment.

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Date and Time are used in our everyday lives. It is important to understand how to use Date and Time in computer programming. You might have to create a website with a calendar. The application should show relevant times based on the user's current timezone. 

JavaScript offers us a d....


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JavaScript is one of the 3 core language technologies of the World Wide Web that all web developers must learn:

1.      HTML to define the content of web pages.

2.      CSS to specify the layout of web pages.

3.      JavaScript to program the behavior of web pages.

JavaScript is a scripting or programming language that allows you to implement complex things on web pages. Every time a web page does more than just sit there and display static information for you to look at, displaying timely content updates, interactive maps, animated 2D/3D graphics, scrolling video jukeboxes, etc. − you can bet that JavaScript is probably involved.


The benefits of using JavaScript are:

1.      You can validate user input before sending the page off to the server. This saves server traffic, which means less load on your server.

2.      Immediate feedback to the visitors − They don't have to wait for a page reload to see if they have forgotten to enter something.

3.      Increased interactivity − You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard.

4.      Richer interfaces − You can use JavaScript to include such items as drag-and-drop components and sliders to give a Rich Interface to your site visitors.


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