{"id":687,"date":"2021-12-03T06:56:39","date_gmt":"2021-12-03T06:56:39","guid":{"rendered":"https:\/\/swatilathia.wordpress.com\/?page_id=687"},"modified":"2025-10-05T08:52:51","modified_gmt":"2025-10-05T08:52:51","slug":"javascript-tutorial","status":"publish","type":"page","link":"https:\/\/swatilathia.com\/?page_id=687","title":{"rendered":"JavaScript Tutorial 1"},"content":{"rendered":"\n

Table of Contents<\/p>\nToggle<\/span>

<\/span>What is JavaScript?<\/strong><\/span><\/h2>\n\n\n\n
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JavaScript (js) is a light-weight object-oriented programming language which is used by several websites for scripting the web pages.<\/li>\n\n\n\n
It is an interpreter, full-fledged programming language that enables dynamic interactivity on websites when applied to an HTML document.<\/li>\n\n\n\n
With JavaScript, users can build modern web applications to interact directly without reloading the page every time.<\/li>\n<\/ul>\n\n\n\n
<\/span>Features of JavaScript<\/strong><\/span><\/h3>\n\n\n\n
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All popular web browsers support JavaScript as they provide built-in execution environments.<\/li>\n\n\n\n
JavaScript follows the syntax and structure of the C programming language.<\/li>\n\n\n\n
JavaScript is an object-oriented programming language.<\/li>\n\n\n\n
It is a light-weighted and interpreted language.<\/li>\n\n\n\n
It is a case-sensitive language.<\/li>\n\n\n\n
JavaScript is supportable in several operating systems including, Windows, macOS, etc.<\/li>\n<\/ol>\n\n\n\n
<\/span>Application of JavaScript<\/strong><\/span><\/h3>\n\n\n\n
JavaScript is used to create interactive websites. It is mainly used for:<\/p>\n\n\n\n
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Client-side validation,<\/li>\n\n\n\n
Dynamic drop-down menus,<\/li>\n\n\n\n
Displaying date and time,<\/li>\n\n\n\n
Displaying pop-up windows and dialog boxes (like an alert dialog box, confirm dialog box and prompt dialog box),<\/li>\n\n\n\n
Displaying clocks etc.<\/li>\n<\/ul>\n\n\n\n
<\/span>JavaScript Syntax<\/strong><\/span><\/h2>\n\n\n\n
JavaScript example is easy to code. JavaScript provides 3 places to put the JavaScript code: within body tag, within head tag and external JavaScript file.<\/p>\n\n\n\n
<html> \n\t<body> \n\t<script type=\"text\/javascript\"> \n\t\tdocument.write(\"We are learning JavaScript \"); \n\t<\/script> \n\t<\/body> \n<\/html><\/code><\/pre>\n\n\n\n\nThe script tag specifies that we are using JavaScript.<\/li>\n\n\n\n The text\/javascript is the content type that provides information to the browser about the data.<\/li>\n\n\n\n The document.write() function is used to display content through JavaScript.<\/li>\n\n\n\n There are 3 places where we can put <script> or JavaScript code:\n\nBody: When page loads, JavaScript runs<\/li>\n\n\n\n Head : When some specific action triggers, JavaScript runs JS (external javascript file): Uses for code re usability<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<\/span>Types of JavaScript Comments<\/strong><\/span><\/h2>\n\n\n\n\nIt is a meaningful way to deliver message. There are two types of comments in JavaScript.<\/li>\n\n\n\n Single-line Comment\u00a0 \/\/<\/li>\n\n\n\n Multi-line Comment\u00a0 \/*\u00a0\u00a0 *\/<\/li>\n<\/ul>\n\n\n\n<\/span>JavaScript Variable<\/strong><\/span><\/h2>\n\n\n\n\nA JavaScript variable is simply a name of storage location<\/li>\n\n\n\n There are two types of variables in JavaScript: local variable and global variable<\/li>\n<\/ul>\n\n\n\n<\/span>Rules to declare a JavaScript variable<\/strong><\/span><\/h3>\n\n\n\n\nName must start with a letter (a to z or A to Z) or underscore.<\/li>\n\n\n\n After first letter we can use digits (0 to 9), for example value1.<\/li>\n\n\n\n JavaScript variables are case sensitive, for example a and A are different variables.<\/li>\n<\/ul>\n\n\n\n<\/span>JavaScript Variable Scope<\/strong><\/span><\/h3>\n\n\n\n\nThe scope of a variable is the region of your program in which it is defined. JavaScript variables have only two scopes.<\/li>\n<\/ul>\n\n\n\n\nGlobal Variable<\/strong> \u2212 A global variable has global scope which means it can be defined anywhere in your JavaScript code.<\/li>\n\n\n\n Local Variable<\/strong> \u2212 A local variable will be visible only within a function where it is defined. Function parameters are always local to that function. Within the body of a function, a local variable takes precedence over a global variable with the same name. If you declare a local variable or function parameter with the same name as a global variable, you effectively hide the global variable.<\/li>\n<\/ol>\n\n\n\n<body>\n\t<script type = \"text\/javascript\">\n var a = \"global\"; \/\/ Declare a global variable\n function fun_scope( ) \n {\n \tvar a = \"local\"; \/\/ Declare a local variable\n document.write(\"The value of a = \",a,\"<br>\");\n }\n\tfun_scope();\n document.write(\"The value of a = \",a); \/\/global\n \t<\/script> \n<\/body><\/code><\/pre>\n\n\n\nOutput<\/strong><\/p>\n\n\n\n\n\t