Javascript block in html page

JavaScript Where To

In HTML, JavaScript code is inserted between tags.

Example

Old JavaScript examples may use a type attribute: .
The type attribute is not required. JavaScript is the default scripting language in HTML.

JavaScript Functions and Events

A JavaScript function is a block of JavaScript code, that can be executed when «called» for.

For example, a function can be called when an event occurs, like when the user clicks a button.

You will learn much more about functions and events in later chapters.

JavaScript in or

You can place any number of scripts in an HTML document.

Scripts can be placed in the , or in the section of an HTML page, or in both.

JavaScript in

In this example, a JavaScript function is placed in the section of an HTML page.

The function is invoked (called) when a button is clicked:

Example

Demo JavaScript in Head

JavaScript in

In this example, a JavaScript function is placed in the section of an HTML page.

The function is invoked (called) when a button is clicked:

Example

Demo JavaScript in Body

Placing scripts at the bottom of the element improves the display speed, because script interpretation slows down the display.

External JavaScript

Scripts can also be placed in external files:

External file: myScript.js

External scripts are practical when the same code is used in many different web pages.

JavaScript files have the file extension .js.

To use an external script, put the name of the script file in the src (source) attribute of a tag:

Example

You can place an external script reference in or as you like.

The script will behave as if it was located exactly where the tag is located.

External scripts cannot contain tags.

External JavaScript Advantages

Placing scripts in external files has some advantages:

• It separates HTML and code
• It makes HTML and JavaScript easier to read and maintain
• Cached JavaScript files can speed up page loads

To add several script files to one page — use several script tags:

Example

External References

An external script can be referenced in 3 different ways:

• With a full URL (a full web address)
• With a file path (like /js/)
• Without any path

This example uses a full URL to link to myScript.js:

Example

This example uses a file path to link to myScript.js:

Example

This example uses no path to link to myScript.js:

Example

You can read more about file paths in the chapter HTML File Paths.

Источник

How to Insert a DIV Block and Other HTML Elements into a Web Page Using JavaScript

I was asked by a visitor how he could programmatically insert a DIV block into his web page using JavaScript. This article shows one way in which this can be done. The method given can also be used for other HTML elements.

Prerequisites

I will assume here that you know some JavaScript and HTML. You do not have to be an expert or anything like that, but some knowledge is needed, otherwise even the question dealt with here will be meaningless to you.

If you do not have a website, and have arrived here thinking that this article will give you an idea of what web development is like, please read How to Create a Website or my articles on domain names instead, since they will be more relevant.

Adding a DIV Block or Other HTML Elements with JavaScript

The following code demonstrates one way to insert a DIV block with JavaScript.

var block_to_insert ;
var container_block ;

block_to_insert = document.createElement( ‘div’ );
block_to_insert.innerHTML = ‘This demo DIV block was inserted into the page using JavaScript.’ ;

container_block = document.getElementById( ‘democontainer’ );
container_block.appendChild( block_to_insert );

Let’s say that the relevant part of the web page has the following HTML.

When the code is executed, that part of the page effectively becomes as follows.

Explanation of the Code

Let’s work through the code, line by line.

The above line sets the content of the DIV block so that it has the words «This demo DIV block was inserted into the page using JavaScript.» It is equivalent to writing the following HTML code.

The above is the bare minimum that you will typically need to do to inject a DIV block into a web page. You will probably need to add additional code, such as to assign your DIV an id and/or class so that you can customize its appearance using CSS, for example, as follows:

Demo

You can see a demo of the code in action by clicking the button below. The same code given above is used here. The outline around the DIV block was added using CSS.

Compatibility

The above code should work in all modern browsers.

Copyright © 2017 Christopher Heng. All rights reserved.
Get more free tips and articles like this, on web design, promotion, revenue and scripting, from https://www.thesitewizard.com/.

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Copyright © 2017 Christopher Heng. All rights reserved.
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This page was last updated on 19 May 2017.

Источник

Блоки в JavaScript

В сей поздний час мою голову посетила одна очень странная мысль. Не долго думая, я решил написать коротенький пост по этому поводу.
Что же, сил и времени на написание второй статьи о WebRTC у меня до сих пор нет, а на пост-заметку я решил все же найти мозговые и временные ресурсы.

Суть мысли, или даже вопроса — почему никто (встречавшийся мне) не использует отдельные блоки кода (помимо тех, которые используются с выражениями if else и т.д.) в своих JavaScript приложениях?

Как создать блок кода в JavaScript?

Чем может быть полезен блок?

В JavaScript блоки кода не создают свою область видимости (скоуп), поэтому будем искать полезность в чем-то другом.
Самое элементарное применение — разделение логических частей кода. Да еще какое! Блок можно использовать с меткой.

Толку с нее в данной ситуации мало. С таким успехом можно заменить метку на комментарий, но ведь как красиво смотрится.
Но остается проблема в ограниченности метки.

Опытный и не очень программист может сказать — все логичные блоки / части кода лучше выносить в отдельные функции. Но попробую сразу же не согласиться. Давайте рассмотрим пример из жизни?
Допустим, есть у меня Backbone приложение. При инициализации каждой view я должен совершать стандартные действия: подписываться на глобальные события, подписываться на изменения модели или коллекции и т.д.

Почему-то я не хочу выносить это в отдельные функции. Я привык, что в методе initialize я могу увидеть сразу подписку на все нужные события.
Так почему же мне не разделить эту массу кода на отдельные логические блоки кода в рамках одного метода и скоупа?

Backbone.View.extend( < initialize: function () < ModelEvents: < this.model.on('change', this.render); this.model.on('add', this.onAdd); this.model.on('change:type', this.onResetType); >AppEvents: < app.subscribe('reload', this.render, this); app.subscribe('remove', this.remove, this); app.subscribe('vodka', this.drink, this); >> >); 

Недостатки

Даже не знаю, какие могут быть недостатки у такого способа разделения кода. Быть может, есть вероятность того, что можно запутаться — перепутать блок кода с объектом. Но у меня такой наклонности не возникает.

Вывод: использовать такие блоки — дело выбора каждого. Комментарии, блоки — кому как нравится. Но хотелось бы все же найти интересное применение таким блокам.

Источник

Style display Property

The display property sets or returns the element’s display type.

Elements in HTML are mostly «inline» or «block» elements: An inline element has floating content on its left and right side. A block element fills the entire line, and nothing can be displayed on its left or right side.

The display property also allows the author to show or hide an element. It is similar to the visibility property. However, if you set display:none , it hides the entire element, while visibility:hidden means that the contents of the element will be invisible, but the element stays in its original position and size.

Tip: If an element is a block element, its display type can also be changed with the float property.

Browser Support

Syntax

Return the display property:

Property Values

Value	Description
block	Element is rendered as a block-level element
compact	Element is rendered as a block-level or inline element. Depends on context
flex	Element is rendered as a block-level flex box. New in CSS3
inline	Element is rendered as an inline element. This is default
inline-block	Element is rendered as a block box inside an inline box
inline-flex	Element is rendered as a inline-level flex box. New in CSS3
inline-table	Element is rendered as an inline table (like ), with no line break before or after the table list-item Element is rendered as a list marker This value sets content before or after a box to be a marker (used with :before and :after pseudo-elements. Otherwise this value is identical to «inline») none Element will not be displayed run-in Element is rendered as block-level or inline element. Depends on context table Element is rendered as a block table (like ), with a line break before and after the table) table-caption Element is rendered as a table caption (like ) table-cell Element is rendered as a table cell (like and ) table-column Element is rendered as a column of cells (like ) table-column-group Element is rendered as a group of one or more columns (like ) table-footer-group Element is rendered as a table footer row (like ) table-header-group Element is rendered as a table header row (like ) table-row Element is rendered as a table row (like table-row-group Element is rendered as a group of one or more rows (like ) initial Sets this property to its default value. Read about initial inherit Inherits this property from its parent element. Read about inherit Technical Details Default Value: inline Return Value: A String, representing the display type of an element CSS Version CSS1 More Examples Example Difference between the display property and the visibility property: function demoDisplay() < document.getElementById(«myP1»).style.display = «none»; > function demoVisibility() document.getElementById(«myP2»).style.visibility = «hidden»; > Example Toggle between hiding and showing an element: function myFunction() < var x = document.getElementById(‘myDIV’); if (x.style.display === ‘none’) < x.style.display = ‘block’; > else < x.style.display = ‘none’; > > Example Difference between «inline», «block» and «none»: function myFunction(x) < var whichSelected = x.selectedIndex; var sel = x.options[whichSelected].text; var elem = document.getElementById(«mySpan»); elem.style.display = sel; > Example Return the display type of a element: Источник Оцените статью Вам также может понравиться Ящики с усами python pandas.plotting.boxplot# Make a box-and-whisker plot Пример использования свойства CSS table-layout. table-layout¶ Свойство table-layout определяет, как Пример использования свойства CSS table-layout. HTML Размеры таблицы HTML таблицы могут иметь разные Пример использования свойства CSS table-layout. table-layout¶ Свойство table-layout определяет, как Правообладателям Политика конфиденциальности Контакты