In JavaScript we find a number of primitiv data types:
In addition we have:
The existing composite (reference) data types in JavaScript are:
The existing special data types in JavaScript are:
The existing special data types in JavaScript are:
A string is a combination of Unicode characters (letters, digits, and punctuation marks). A string usually represent a text in JavaScript and it's single or double quotation marks. Double quotation marks can be used in strings surrounded by single quotation marks. Single quotation marks can be used in strings surrounded by double quotation marks:
"Hallo there; today is friday!" '"This is a nice car!" said the old man.' "99" 'y'
JavaScript does not have a type for just one single character. This is solved by using a string of only one character.
JavaScript number can be either an integer or a floating-point values. In JavaScript, there is no distinction between them.
Integer values can be represented as positive whole numbers, negative whole numbers, in addition to 0. They can be in base 10 (decimal), base 16 (hexadecimal), and base 8 (octal). Usually the numbers in JavaScript are written in decimal.
Floating-point values can represented as whole numbers with decimals. They can also be expressed in scientific notation and that means as an uppercase or lowercase "e" is used as "ten to the power of".
| Number | Description | Decimal Equivalent |
|---|---|---|
| .0001, 0.0001, 1e-4, 1.0e-4 | Four equivalent floating-point numbers. | 0.0001 |
| 3.45e2 | A floating-point number. | 345 |
| 45 | An integer. | 45 |
| 0378 | An integer. Although this looks like an octal number (it begins with a zero), 8 is not a valid octal digit, so the number is treated as a decimal. | 378 |
| 0377 | An octal integer. Notice that although it only appears to be one less than the number above, its actual value is quite different. | 255 |
| 0.0001 | A floating point number. Even though this begins with a zero, it is not an octal number because it has a decimal point. | 0.0001 |
| 00.0001 | This is an error. The two leading zeros mark the number as an octal, but octals are not allowed a decimal component. | N/A (compiler error) |
| 0Xff | A hexadecimal integer. | 255 |
| 0x37CF | A hexadecimal integer. | 14287 |
| 0x3e7 | A hexadecimal integer. Notice that the 'e' is not treated as exponentiation. | 999 |
| 0x3.45e2 | This is an error. Hexadecimal numbers cannot have decimal parts. | N/A (compiler error) |
JavaScript also have numbers with special values. These are:
The string and number data types can have an unlimited number of different values. The Boolean data type can only have two different values and they are the literals true and false. A Boolean value will specify if a condition is true or false.
Comparisons you make in your scripts always have a Boolean outcome. Consider the following line of JavaScript code.
//How to use boolean values in a control structure. if (x == 100) { z = z + 1; } else { x = x + 1; }
In JavaScript the data type null has only one value and that is: null.
A variable that contains null has no valid Number, String, Boolean, Array, or Object. It is possible to erase the content of a variable by assigning it to null without erasing the variable.
As in C and C++ null is the same as 0.
var x; // This method works. if (x == undefined) { document.write ( "comparing x to undefined <br/>"); } // This method doesn't work - you must check for the string "undefined". if ( typeof (x) == undefined) { document.write ( "comparing the type of x to undefined <br/>" ); } // This method does work. if ( typeof (x) == "undefined") { document.write ( "comparing the type of x to the string 'undefined'"); } // Output: // comparing x to undefined // comparing the type of x to the string 'undefined'
Bitwise operators will handle their operands as a sequence of 32 bits (zeroes and ones), and not like decimal, hexadecimal, or octal numbers. For example, the decimal number nine has a binary representation of 1001. Bitwise operators perform their operation....
Scope determines if variables are accessible (visible).
A scope in JavaScript defines what variables you have access to. There are two kinds of scope – global scope and local scope.
Function scope and block scope are local scope - variables declared inside a function or a bl....
Developer Tools are tools that are a part of most modern web browsers.
Every Web Developer should know how to use the tools. The tools do a range of things, from inspecting currently-loaded HTML, CSS and JavaScript to showing which assets the page has requested and how long they took to l....
JavaScript have a Random number function. The method can generate a number in a specific range. The number can not be reasonably be predicted.
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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