It's possible to use typeof in angularjs?
I have an ngrepeat that loop trough my data and should check if data is string or object.
<tr ng-repeat="text in data">
<td>{{angular.isObject(text) && 'IsObject'||text}}</td>
</tr>
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2 Answers
Please don't use a filter in this case, it's clearly a place for a function in your controller:
<tr ng-repeat="text in data">
<td>{{isThisAnObject(text)}}</td>
</tr>
And in your controller:
$scope.isThisAnObject = function(input) {
return angular.isObject(input) ? 'IsObject' : input;
};
It's not only less code, but it also works better in many other places. Filters are for a very specific purpose. Not this!
5 Comments
Nick Perkins
Can you explain why, in this case, a function is better than a filter? What is this "very specific purpose" for filters that makes them a poor choice for this?
Zorgatone
yeah please I'd like a better explanation for this @TomBull
Tom Bull
A filter, as the name suggests, is designed for filtering. Specifically, filtering arrays - i.e. restricting the items shown in, say, a repeater. It is a (presumably unintended) side-effect that the syntax also works on individual items as in the accepted answer. Although the syntax shown works fine in the simplest case - it quickly gets messy. For example, what happens when you want to compose more than one of these operations? Or process the results of the operation in some other way? Or use the operation in some other context?
Tom Bull
Note all of my examples of where a filter breaks down have some (often very convoluted) workaround - but this really is a case of using the most appropriate tool for the job. A function (possibly in a shared library) that is exposed by the controller is the most sensible thing to use in this case.
dror
angular filters are not only for filtering data, but also for formatting data to a sensible string. Some native angular filters work like that. For example, the currency filter: docs.angularjs.org/api/ng/filter/currency
Sounds like a good place to use a filter:
<tr ng-repeat="text in data">
<td>{{text|displayText}}</td>
</tr>
angular.module('myApp').filter('displayText', function() {
return function(text) {
return angular.isObject(text) ? 'IsObject' : text;
};
});
2 Comments
Tom Bull
Actually, it's a pretty bad place to use a filter. This is not what filters were intended for and can lead to some seriously poor code if you continue to use the filter elsewhere in a similar way. A better way would be to use a function.
Zorgatone
@TomBull why is that bad to use a filter in this case?