Skip to main content

ES6: let vs var

The 'let' keyword was introduced in ES6 to help clarify intent.

The 'var' keyword should keep a variable visible within it's block, only.
But in fact, it was attached to the function it is declared in, via hoisting.
Which means it could be accessed outside of it's block.

The 'let' keyword was then introduced to make clear that a variable declared within a block, is only visible within this block.
As opposed to 'var' who could be visible outside of that block.

Comments

Post a Comment

Popular posts from this blog

React JS Patterns

React JS is always evolving, and evolving quickly. These evolutions can be very significant ones, for example, the addition of hooks. React has a lot of code patterns, often these patterns are motivated by the DRY and/or the open-close principle. These patterns sometimes come in to replace a previous one, yet the previous ones still stays in use, as a consequence, the list of patterns keep growing. The goal of the next few posts will be to list the patterns commonly used in React JS developpement. Some patterns are more specific to JSX and I will start with these, and maybe add patterns specific to Redux.
4 comments
Read more

70-562 ListView

List View is a versatile control that allows to work with a signle control rather than many smaller controls. Provides rich sorting, deleting, editing, it is one of the most flexible grid control. Design view can fill the ListView with fake data to give an overview. In designer, the configure list view link might not show, (currently a bug), to fix configure the datasource but cancel then click configure datasource again and this time click finish and the Cofnoigure ListView link will show up in the smarttag. You can choose templates, LayoutTemplate is crucial, ItemTemplate(a row is part of a table, in a list view they are called items since they don't have to correspond to a table row), AlternatingItemTemplate, ItemSeparatorTemplate, SelectedItem, EmptyItemTemplate, EditItemTemplate, InsertItemTemplate allows to customize what the user will be presented when creating an item, EmptyDataTemplate. The itemPlaceHolder and the groupPlaceHolder are important elements as the will b...
Post a Comment
Read more

70-562 Web Services

A single server can't handle it all, connecting many computers together is far more powerfull than in a mainframe. In distributed applications, One cluster may be for the database, then a group of servers might function as a specialized application server, and still others handle user interface and security logic. All those computers need to communicate together. There are 4 broad WS technollgies, 1) Universal access: The tcp/ip is most common protocol 2) Standard data representation: xml is intended to transport data. And XPath that allows to xtract a subset of data easily, while http was made for to transport markup(html). While 3) Standard message format: SOAP stadardizes the message envelope 4) Service description format: WSDL web services description language The web service has to derive from System.Webh.Services.WEbService and contain the WebSErvice and WebSErviceBinding attribute. The WebMethod attribute is added to each methods exposed to the outside world. T...
Post a Comment
Read more