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Sana | 15.04.2024 | Hajmi | 225.5 Kb. | | #195581 |
Bog'liq JS PPt Doc1, Raqamli Innovatsion texnologiyalarning O’zbekiston turizmining drayveri sifatida, t. b, KPxl4B6XkgP8f9mdLYyJwlkOPoftmxWMbUEYSabO, 1032919 JavaScript Basics - What is JavaScript?
- JavaScript is a programming language designed for Web pages.
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- By: O`sarov Alisher 051-23 - guruh
Why Use JavaScript? - JavaScript enhances Web pages with dynamic and interactive features.
- JavaScript runs in client software.
- JavaScript 1.3 works with version 4.0 browsers.
What Can JavaScript Do? - Common JavaScript tasks can replace server-side scripting.
- JavaScript enables shopping carts, form validation, calculations, special graphic and text effects, image swapping, image mapping, clocks, and more.
JavaScript Syntax. - Unlike HTML, JavaScript is case sensitive.
- Dot Syntax is used to combine terms.
- e.g., document.write("Hello World")
- Certain characters and terms are reserved.
- JavaScript is simple text (ASCII).
JavaScript Terminology. - JavaScript programming uses specialized terminology.
- Understanding JavaScript terms is fundamental to understanding the script.
- Objects, Properties, Methods, Events, Functions, Values, Variables, Expressions, Operators.
Objects - Objects refers to windows, documents, images, tables, forms, buttons or links, etc.
- Objects should be named.
- Objects have properties that act as modifiers.
Properties - Properties are object attributes.
- Object properties are defined by using the object's name, a period, and the property name.
- e.g., background color is expressed by: document.bgcolor .
- document is the object.
- bgcolor is the property.
Methods - Methods are actions applied to particular objects. Methods are what objects can do.
- e.g., document.write(”Hello World")
- document is the object.
- write is the method.
Events - Events associate an object with an action.
- e.g., the OnMouseover event handler action can change an image.
- e.g., the onSubmit event handler sends a form.
- User actions trigger events.
Functions - Functions are named statements that performs tasks.
- e.g., function doWhatever () {statement here}
- The curly braces contain the statements of the function.
- JavaScript has built-in functions, and you can write your own.
Values - Values are bits of information.
- Values types and some examples include:
- Number: 1, 2, 3, etc.
- String: characters enclosed in quotes.
- Boolean: true or false.
- Object: image, form
- Function: validate, doWhatever
Variables - Variables contain values and use the equal sign to specify their value.
- Variables are created by declaration using the var command with or without an initial value state.
- e.g. var month;
- e.g. var month = April;
Expressions - Expressions are commands that assign values to variables.
- Expressions always use an assignment operator, such as the equals sign.
- e.g., var month = May; is an expression.
- Expressions end with a semicolon.
Operators - Operators are used to handle variables.
- Types of operators with examples:
- Arithmetic operators, such as plus.
- Comparisons operators, such as equals.
- Logical operators, such as and.
- Control operators, such as if.
- Assignment and String operators.
Methods of Using JavaScript. - 1. JavaScripts can reside in a separate page.
- 2. JavaScript can be embedded in HTML documents -- in the , in the , or in both.
- 3. JavaScript object attributes can be placed in HTML element tags.
1. Using Separate JavaScript Files. - Linking can be advantageous if many pages use the same script.
- Use the source element to link to the script file.
2. Embedding JavaScript in HTML. - When specifying a script only the tags and are essential, but complete specification is recommended:
Using Comment Tags - HTML comment tags should bracket any script.
- The tags hide scripts in HTML and prevent scripts from displaying in browsers that do not interpret JavaScript.
- Double slashes // are the signal characters for a JavaScript single-line comment.
3. Using JavaScript in HTML Tags. - Event handlers like onMouseover are a perfect example of an easy to add tag script.
- onMouseover="document.logo.src='js2.gif'"
- onMouseout="document.logo.src='js.gif'">
Creating an Alert Message - The following script in the tag uses the onLoad event to display an Alert window
- The message is specified within parenthesis.
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