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What is the purpose of $ q.when in angularjs?

I have read the documentation for $ q.when in the official angular docs, but I still don't understand what the purpose of $ q.when is and how the response is managed.

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$q.when

takes a promise or simple value and converts it to a promise. If it's already a promise, it just returns it.

This is useful if you don't know if the object you are dealing with is a promise or not. For example, you might have an if / else statement where one path returns a promise, but another path returns a value directly. In this case, it would be useful to use $q.when

to handle the return so that you get a value from it, whether it's a promise or not.



For example:

function getData(){
    if(cachedData) return $q.when(cachedData); // converts to promise
    else return $http.get("/dataUrl"); // make HTTP request, returns promise
}
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