How to write alert function in javascript

JavaScript allows us to write our own functions as well. If the user clicks "Cancel" the box returns null. If the user clicks "OK", the box returns true.

Now it takes two parameters. A function contains code that will be executed by an event or by a call to that function. Because of this weird behavior, and because function names are case sensitive, it makes sense to have a different convention for naming functions than for naming variables.

In its simplest form, function is just a shorthand name for a series of JavaScript instructions. An Example of a Simple Function Figure shows you how the window-centering code in Figure looks rewritten as a web page containing a function.

Syntax The basic syntax is shown here. Next Page A function is a group of reusable code which can be called anywhere in your program. No other characters, including spaces, are allowed. But there is a facility to pass different parameters while calling a function.

So, functions that are going to return a value must use the return statement. We have modified our sayHello function here. To add a space between two string variables, insert a space into the expression, OR in one of the strings.

If the variable visitor is not equal to PRES, then put the string "Dear " into the variable named greeting. The solution to these problems is to give all the JavaScript in Figure a name and then simply call that name when you want to open and center a window. The word function must be written in lowercase letters, otherwise a JavaScript error occurs!

Names in this notation style consist of strings of words without spaces, in which every word except the first is initial-capitalized, as in openAndCenterTheWindowmyCatand printDate.

Knowing how to write your own functions will improve almost any JavaScript you create. The first character must be a letter; the rest of the characters can include letters, numbers, dashes, and underscores. This eliminates the need of writing the same code again and again.

Even more problematic, if you want to change the code to affect window size or centering, you have to make the change everywhere you put the link.

When a confirm box pops up, the user will have to click either "OK" or "Cancel" to proceed. When you call the alert function, JavaScript under stands it as a command to carry out some task, such as opening a window that has an OK button and a close button and putting some text in the window. Example Try the following example.

The rules for naming a function are similar to those for naming a variable. When a prompt box pops up, the user will have to click either "OK" or "Cancel" to proceed after entering an input value.

Writing Your Own JavaScript Functions

In-caps notation is a pretty common convention and should serve you well. Do not forget about the importance of capitals in JavaScript! Opening and centering a window using a function Page 1 of 2. The return Statement The return statement is used to specify the value that is returned from the function.

Also note that you must call a function with the exact same capitals as in the function name. A function can take multiple parameters separated by comma. A function with no parameters must include the parentheses after the function name: These passed parameters can be captured inside the function and any manipulation can be done over those parameters.

For example, you can pass two numbers in a function and then you can expect the function to return their multiplication in your calling program. Function Definition Before we use a function, we need to define it. You could write a link resembling Figure most of the code in it is similar to Figure Now, the script is not executed before the user hits the button.Like variables, function names are case sensitive, so JavaScript will consider a function called feedTheCat() to be different from a function called FeedTheCat().

Make sure you don't give a function and a variable the same name. A JavaScript function is defined with the function keyword, followed by a name, followed by parentheses ().

Function names can contain letters, digits, underscores, and dollar signs (same rules as variables). Note: many of the contents of this page are taken from w3school website.

JS - Operators, Popups, Function

Operators Arithmetic Operators. The most common way to define a function in JavaScript is by using the function keyword, followed by a unique function name, a list of parameters (that might be empty), and a statement block surrounded by curly braces.

Well organized and easy to understand Web building tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, PHP, and XML.

How TO - Alerts Alerts. Alert messages can be used to notify the user about something special: danger, success, information or warning.

How TO - Alerts

JS Functions Function Definitions JavaScript has three kind of popup boxes: Alert box, Confirm box, and Prompt box. Alert Box.

An alert box is often used if you want to make sure information comes through to the user. When an alert box pops up, the user will have to click "OK" to proceed. Syntax.

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How to write alert function in javascript
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