Важно обратить внимание, что на подгрузку данных «в фоне» потребовалось некоторое время. В реальных проектах нужно учитывать эту особенность и правильно распределять зависимости последовательностей отдачи содержимого пользователю.

Может оказаться так, что при формировании финансового графика часть данных не успеет прийти вовремя — это исказит трактование данных из отчёта и навредит бизнесу из-за ошибки вычислений. Будьте внимательны! В таких случаях уместно использовать объект Promise .

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How to access HTML elements in JavaScript?

In HTML, sometimes the user needs to access the HTML elements to display the user different changes. We can support this by using modern-day JavaScript. To facilitate this, we can move ahead and change the HTML element by using the following techniques −

• Get HTML element by Id
• Get HTML element by className
• Get HTML element by Name
• Get HTML element by tagName
• Get HTML element by CSS Selector

Below we have added the demonstration for the above methods.

Get HTML element by Id

This method gets the element from a unique ID and lets the user access that element. Users can use the getElementById() method to access and update the HTML content. If any element does not exist with the given Id, the method returns null.

Syntax

document.getElementById(element_ID);

Parameter − It takes the element id for the element to be accessed.

Return value − It returns the object with the particular id. If the element with the particular id doesn’t exist, null is returned.

Example 1

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DOM getElementById() Method
  

Output

Get HTML element by className

This selects the element from the class name. We can provide a class name to each element in HTML and then access the same using that class name. In this we are going to use the method getElementsByClassName() to get and update the element.

Syntax

document.getElementsByClassName(classnames);

Parameter − It takes input for class names of the element that needs to be accessed.

Return value − It returns the collection of objects that have a particular class name. Users can access this collection using the indexes.

Example 2

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DOM getElementsByclassName() Method   

Output

Get HTML element by Name

In JavaScript, we can access elements by using the getElementsByName() method. It helps the user to get an element with the help of a name. The name here is the attribute name of the HTML element.

Syntax

document.getElementsByName(element_name);

Parameter − It takes input for the name of the element that the user wants to access.

Return value − It returns the collection of elements that have a particular name.

Example 3

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DOM getElementsByName() Metho
   

Output

Get HTML elements by TagName

In JavaScript, we can use the getElementsByTagName() method to access all the elements with the given tag name. This method is the same as the getElementsByName() method. Here, we are accessing the elements using the tag name instead of using the name of the element.

Syntax

document.getElementsByTagName(Tag_name);

Parameter − It takes input for the tag name

Return value − It returns the collection of elements that includes the tag name passed as a parameter.

Example 4

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DOM getElementsByTagName() Method
   

Output

Get HTML elements by CSS Selector

We can select the HTML elements by using the CSS selectors such as class Id, and tagName. HTML elements can be retrieved using CSS selectors in two ways. The querySelector() method returns the first element that matches the particular CSS selector. The querySelectorAll() method returns all element that matches the particular CSS selector.

Syntax

document.querySelector(selectors); document.querySelectorAll(selectors);

Parameter − As a parameter, it accepts different CSS selectors such as class, tag name, and id.

Return value − The querySelector() method returns the first object that matches thecCSS selectors, while the querySelectorAll() method returns a collection of all objectscthat match the CSS selectors.

Example 5

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