Expert JavaScript Developer

The pop() method is similar as the shift() method but the difference is that the Shift method works at the start of the array. Also the pop() method take the last element off of the given array and returns it. The array on which is called is then altered.

Example:

var cloths = ["Shirt", "Pant", "TShirt"];

cloths.pop();

//Now cloth becomes Shirt,Pant

To set up your own JavaScript error handler some optional parameters has to be known. These parameters are as follows:

- Textual description of error

- Address (URL) of page on which error occurred

- Number of line in which error occurred

If you want to invoke the default error handler of the browser, then your function should return (false) or vice versa. Example code:

function handlerFunction(description,page,line)

{ // put error-handling operators here

return true;}

window.onerror=handlerFunction;

► The variable which are declared in the program but not assigned any value yet is called undefined variable while the variable which are not declared in the program is called undeclared variable.

► For Example :

undeclared variable:

<script>

var p;

alert(p); // This will give error because p is undeclared variable.

</script>

? undefined variable

<script>

alert(p); //This will give error because p is undefined.

</script>

JavaScript, some also know it as ECMAScript, is a dynamic programming language used in a web development. It is an integral part of web browsers, and it allows, among other things, better user interaction, browser control, client-server communications (synchronous and asynchronous), alterations of displayed DOM content.

Although it was first introduced under a different name (Mocha), during its initial release it was officially named LiveScript. Developed by Netscape, the first version was available in Navigator 2.0 (September 1995), but it was renamed JavaScript in version 2.0B3.

► The escape() function is used to encode the string to convert it as portable string so that it can be sent across any network to any computer which supports ASCII characters.

► This function encodes special characters, with the exception of @ * + - / . _

► Syntax :

escape(string1)

Where string1 is the string to be encoded.

► Example :

<script>

document.write(escape("Questions? Get from us!"));

</script>

► Output :

Questions%3F%20Get%20from%20us%21

There are three types of errors:

► Load time errors: Errors which come up when loading a web page like improper syntax errors are known as Load time errors and it generates the errors dynamically.

► Run time errors: Errors that come due to misuse of the command inside the HTML language.

► Logical Errors: These are the errors that occur due to the bad logic performed on a function which is having different operation.

Return value of prompt() function depends on browsers. Most of the browsers return the value as null and some return as empty string (" "). IE is one of the browser which gives the error of empty string when clicked the cancel button by the user, otherwise all the recent browser return the value as null. The code to check this is as follows:

userInput = prompt('Prompt text','Suggested input');

if (userInput) {

// do something with the input

}

Setting timers allows you to execute your code at predefined times or intervals.

This can be achieved through two main methods: setInterval(); and setTimeout();

setInterval() accepts a function and a specified number of milliseconds.

ex) setInterval(function(){alert("Hello, World!"),10000) will alert the "Hello, World!" function every 10 seconds.

setTimeout() also accepts a function, followed by milliseconds. setTimeout() will only execute the function once after the specified amount of time, and will not reoccur in intervals.

► The push() method is used to append one or more elements to the end of an array.

► For example :

var fruits = [ "apple" ];

fruits.push( "banana" );

fruits.push( "mango", "strawberry" );

console.log(fruits);

► We get the following console output :

["apple ", "banana ", "mango ", "strawberry "]

► Using Push() method we can also append multiple elements by passing multiple arguments.

► The elements will be appended in the order of they are inserted i.e. left to right.

Both are almost similar. JavaScript is developed by Netscape and Jscript was developed by Microsoft.

This can be done by including the name of the required frame in the hyperlink using the 'target' attribute.

<a href="newpage.htm" target="newframe">>New Page</a>

Using strict mode enforces stricter error handling when running your code. It essentially raises errors that would have otherwise failed silently. Using strict mode can help you avoid simple mistakes like creating accidental globals, undefined values, or duplicate property names. This is typically a good idea when writing JavaScript, as such errors can create a lot of frustrating side effects and be difficult to track down.

► The shift() method is similar as the pop() method but the difference is that Shift method works at the beginning of the array.

► The shift() method take the first element off of the given array and returns it. The array on which is called is then altered.

► For example :

var myarray = ["apple ", "banana ", "mango "];

console.log(myarray.shift());

console.log(myarray);

► We get the following console output :

apple

["banana ", "mango "];

► When we call shift() on an empty array, it will return an undefined value.

► The screen object can be used to retrieve the information about the visitor's screen.

► There are following properties of Screen objects :

avalHeight : This property returns the height of the screen excluding the windows taskbar.

availWidth : This property returns the width of the screen excluding the windows taskbar.

colorDepth : This property returns the bit depth of the color palette to display images.

height : This property returns the total height of the screen.

pixelDepth : This property returns the color resolution of the screen in bits per pixel.

width : This property returns the total width of the screen.

Yes, absolutely. For example, the function getElementById is not the same as the function getElementbyID. Keeping your capitalization consistent is important.

ECMAScript is nothing but another name for JavaScript. Precisely, ECMAScript is the formal name of JavaScript, when XML elements have to be accessed.

Nan is literally "Not-a-Number". NaN usually results when either the result or one of the values in an operation is non-numeric. Even though NaN is not a number, 'console.log(typeof NaN === "number");' logs true, while NaN compared to anything else (including NaN) logs false. The only real way to test if a value is equal to NaN is with the function 'isNaN()'.

'and' operator: &&

'or' operator: ||

'not' operator: !