如何使用ng-if测试变量是否已定义 [英] How to use ng-if to test if a variable is defined
问题描述
有没有一种方法可以使用ng-if来测试是否定义了一个变量，而不仅仅是它是否真实?
Is there a way to use ng-if to test if a variable is defined, not just if it's truthy?
在下面的示例中(实时演示)，HTML仅显示红色商品的运费，因为item.shipping既定义又非零.我还想显示蓝色项目的费用(已定义装运，但为零)，而不显示绿色项目的费用(未定义装运).
In the example below (live demo), the HTML displays a shipping cost for the red item only, because item.shipping is both defined and nonzero. I'd like to also display a cost for the blue item (shipping defined but zero), but not for the green item (shipping not defined).
JavaScript:
JavaScript:
app.controller('MainCtrl', function($scope) {
$scope.items = [
{
color: 'red',
shipping: 2,
},
{
color: 'blue',
shipping: 0,
},
{
color: 'green',
}
];
});
HTML:
<body ng-controller="MainCtrl">
<ul ng-repeat='item in items'>
<li ng-if='item.color'>The color is {{item.color}}</li>
<li ng-if='item.shipping'>The shipping cost is {{item.shipping}}</li>
</ul>
</body>
我尝试做ng-if='angular.isDefined(item.shipping)'，但是没有用. ng-if='typeof(item.shipping) !== undefined'也没有.
I tried doing ng-if='angular.isDefined(item.shipping)', but it didn't work. Nor did ng-if='typeof(item.shipping) !== undefined'.
推荐答案
尝试一下:
item.shipping!==undefined
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