AngularJS Expression From a String

Question

Note: Similar to: angularjs execute expression from variable except I don't want to clutter up my scope with all the possibilities and data sets in use.

I want to be able to utilize pre-determined formulas in Angular's expressions.

Example:

  var config = {
    "Test": {
      name: "test",
      formula: true,
      formulaValue: "item['propertyOne'] + item['propertyTwo']"
    }
  }

<div ng-repeat="item in myArray">
  <span ng-if="config[item.name].formula">{{config[item.name].formulaValue}}</span>
</div>

Where the formula in formulaValue gets evaluated as if I typed it like:

<div ng-repeat="item in myArray">
  <span>{{item['propertyOne'] + item['propertyTwo']}}</span>
</div>

How would I accomplish this? It's not quite feasible to make a $scope function for each type of formula either, as these are setup in a config in fairly large quantities.

Are you saying that this config is already built and has to use that string format? Or can the config be restructured? — charlietfl
– charlietfl, Commented Jun 29, 2016 at 0:05
It can be restructured. The example is very simple and does not fully represent it, just the gist of it. — Douglas Gaskell
– Douglas Gaskell, Commented Jun 29, 2016 at 0:11
Can use eval() on that but due to security is always best to avoid eval. For concatenation a property that has just field names in array would be more ideal in the config — charlietfl
– charlietfl, Commented Jun 29, 2016 at 0:13

charlietfl · Accepted Answer · 2016-06-29 00:43:15Z

1

Not the most ideal config setup but worst case you would need to use eval() which is not well liked due to security

Something like:

function parseConfig(item, configKey){
   if(config[configKey].formula){
      return eval(config[configKey].formulaValue);
   }
}
$scope.parseConfig = parseConfig;

Would put that in a service with your config but for now will just put on scope.

In view would be something like

{{parseConfig(item, 'Test')}}

If it was me I would prefer a config that looked something like

  var config = {
    "Test": {
      name: "test",
      formula: true,
      formulaType: 'concat',
      formulaValue: ['propertyOne','propertyTwo']
    }

then you would check formulaType and do what is needed with the properties in the formulaValue without using eval()

edited Jun 29, 2016 at 0:43

answered Jun 29, 2016 at 0:15

charlietfl

172k14 gold badges125 silver badges154 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Douglas Gaskell Over a year ago

In some cases I may end up having to use eval for more complex operations, however having a formula type and tailoring some functions to handle each type would not be too bad. However, I'll probably end up having to eval some formulas. If I have full control over the config, what is the security concern with eval in this case?

charlietfl Over a year ago

easy to search and find lots about using eval().

Collectives™ on Stack Overflow

AngularJS Expression From a String

1 Answer 1

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related