未加星标

An Introduction to Structural Directives: *ngIf & *ngFor

字体大小 | |
[前端(javascript) 所属分类 前端(javascript) | 发布者 店小二05 | 时间 2017 | 作者 红领巾 ] 0人收藏点击收藏

In this video tutorial, we cover the concept of using structural directives like *ngIf , *ngFor , and *ngSwitchCase in Ionic 2. Structural directives are an Angular concept, but we will be discussing them in the context of an Ionic application. In short, a structural directive allows us to add or remove content to our applications based on some condition.

We will walk through a few basic examples, and also discuss why we use the weird star syntax for structural directives.

Here’s the video :

Video Notes Directives preceded with a * like *ngIf , *ngFor , and *ngSwitchCase are structural directives Structural directives modify the DOM by adding or removing certain elements If an element is removed, it is completely removed rather than just being hidden. This has performance benefits as Angular no longer has to perform change detection for the element The * syntax is used as a shortcut for creating template tags The *ngIf structural directive will remove or show an element based on whether the variable it is bound to evaluates to true or false The *ngFor structural directive will loop over an array of data and create a DOM element for each element in the array, stamping it with the specific values for each array element (if interpolations are being used) The *ngSwitchCase structural directive will test if the value it is bound to matches the value being switched, and if it matches it will display the element (kind of like having multiple *ngIf directives, but cleaner)

本文前端(javascript)相关术语:javascript是什么意思 javascript下载 javascript权威指南 javascript基础教程 javascript 正则表达式 javascript设计模式 javascript高级程序设计 精通javascript javascript教程

分页:12
转载请注明
本文标题:An Introduction to Structural Directives: *ngIf & *ngFor
本站链接:http://www.codesec.net/view/532219.html
分享请点击:


1.凡CodeSecTeam转载的文章,均出自其它媒体或其他官网介绍,目的在于传递更多的信息,并不代表本站赞同其观点和其真实性负责;
2.转载的文章仅代表原创作者观点,与本站无关。其原创性以及文中陈述文字和内容未经本站证实,本站对该文以及其中全部或者部分内容、文字的真实性、完整性、及时性,不作出任何保证或承若;
3.如本站转载稿涉及版权等问题,请作者及时联系本站,我们会及时处理。
登录后可拥有收藏文章、关注作者等权限...
技术大类 技术大类 | 前端(javascript) | 评论(0) | 阅读(77)