trying to reuse a function for getJSON

Question

So here is my situation...

I'm coding something that has several API calls ( I'm at 10 now, and still growing ), that each use a separate function.

The functions all look similar to:

var today = new Date();
specificArray.length = 0;
$.getJSON("https://api-location1", function (data) {
    $.each(data, function (key, value) {
        specificArray[value.ID] = new Instance(value.ID, value.Name, {etc...});
    });
});
localStorage.setItem('lsItem1', today.toString());
localStorage.removeItem('aTable');
localStorage.setObject('aTable', specificArray);

The only things that differ in the various functions are the specificArray being modified from the JSON call, the api-address of a given call, the localStorage key references, and the number of items being passed in to the given Instance (which I use here as a generic name - each function has a different "new Instance" call. ( such as new Employee, new Project, new Product, etc ).

Now, I've tested this by creating a single function that passes in an object that contains all these various items, and uses an eval in the specifiedArray call...

myValues.table = 'aTable'; 
myValues.item = 'lsItem1';
myValues.apicall = 'https://api-location1'
myValues.id = 'value.ID';
myValues.instance = 'new Instance(value.ID, value.Name, {etc...})';
myAPICall(specifiedArray, myValues);

function myAPICall(theArray, someValues) {
  var today = new Date();
  theArray.length = 0;
  $.getJSON(someValues.apicall, function (data) {
    $.each(data, function (key, value) {
      specificArray[eval(someValues.id)] = eval(someValues.instance);
    });
  });
  localStorage.setItem(someValues.item, today.toString());
  localStorage.removeItem(someValues.table);
  localStorage.setObject(someValues.table, theArray);
}

And this seems to work fine - but the concern I have is the eval - which from everything I've read is evil and shouldn't be used - but on the same token - I think this is a good use of it, as its only evaluating specific strings assigned in code in a different function...

Or is there some better way to do this that I'm working around?

Thanks in advance...

NEW EDIT: Here is a JSFiddle that I'm using as an example - http://jsfiddle.net/e876q/

PLEASE NOTE: if I don't use the eval then this doesn't bring up the correct response when clicking the button!

ADDITIONAL EDIT : Here is a LiveWeave that is the same example ( My office blocks JSFiddle from running but not LiveWeave... go figure) http://liveweave.com/wf1oAU

Answer 1

After researching and trying different things, this is what worked for me...

I changed myValues.instance from

myValues.instance = 'new Instance(value.ID, value.Name, {etc...})';

to

myValues.instance = function (v) { this.table[v.someID] = new Instance(v.someID, v.someData);
myValues.table = [];

and then in my json function, i did:

$.getJSON(someValues.apicall, function (data) {
  $.each(data, function (key, value) {
    someValues.instance(value);
  }
}

which worked perfectly.

Thanks to everyone who submitted answers. Special thanks to GRaAL who got me on the right track talking about functions.

DocKraz

Answer 2

You don't need to use eval here. Just pass the objects you're working on directly — no need to be passing strings around.

Answer 3

Instead of eval you may use functions, like this way (I omit some details of your script):

myValues.id = function getId(value) { return value.ID;}
myValues.instance = function createInstance(value) { return new Instance(...)}
myAPICall(specifiedArray, myValues);

function myAPICall(theArray, someValues) {
  $.getJSON(someValues.apicall, function (data) {
    $.each(data, function (key, value) {
      specificArray[someValues.id()] = someValues.instance();
    });
  });
}

it will be more flexible I think. Also if you often use the myAPICall with different parameters that could be a good idea to have a functions factory, like this:

function myAPICallCreator(someValues) {
    return function(theArray) {
       //...
       $.getJSON(someValues.apicall, function (data) {
          $.each(data, function (key, value) {
             specificArray[someValues.id()] = someValues.instance();
          });
       });
       //...
    }
}

var callFunction1 = myAPICallCreator({id: ..., instance: ..., apicall: ...});
var callFunction2 = myAPICallCreator({...});

//...

callFunction1(array1);
callFunction2(array2);