Angular.js ng-switch-测试值是否为空或未定义 [英] Angular.js ng-switch ---testing if value is empty or undefined

问题描述

在Angular.js模板中，我需要测试值是否未定义或为空....由于ng-switch-when测试字符串中的表达式，因此我不确定如何执行此操作.我需要使用ng-switch，因为这是一个if else条件.有什么想法吗?

In Angular.js templating, I need to test if a value is undefined or empty.... I am not sure how to do this since ng-switch-when tests for expressions in strings. I needed to use ng-switch because it's a if else condition. Any ideas?

<div ng-switch="vipLabel">
  <div ng-switch-when="vipLabel.toString()">
    <h1>Getting infomration...one sec</h1>
  </div>
    <div ng-switch-default>
      <h3>Do you wish to unbind {{node.label}} from {{ vipLabel }}?</h3>
    </div>
</div>

推荐答案

ng-switch允许表达式，可以使用占位符，例如:

ng-switch allows expressions, you can use placeholder, as such:

<div ng-switch="selection || '_undefined_'" >      
      <span ng-switch-when="_undefined_">I am set to zero or undefined?!</span>      
      <span ng-switch-default>This string is not empty</span>
</div>

有关更多信息:在空字符串上进行ng-switch

您通常在控制器内执行此操作(请参见链接线程中的答案1).

You usually do it within controller(see answer#1 in linked thread).

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