CODEWITHSUNDEEP
javascriptjson
Max
Max

Reputation: 442

Configure function from JSON file

I have a function that looks like this :

const comparer = (otherArray) => {
  return function (current) {
    return (
      otherArray.filter(function (other) {
        return (
          other.Random_1== current.Random_1 &&
          other.Random_2 ==
            current.Random_2 
            ...
        );
      }).length == 0
    );
  };
};

I want to make it configurable from a JSON file like this :


{
     "matchingRules": {
         "rule_1" : "other.Random_1 == current.Random_1",
         "rule_2" : "other.Random_2 == current.Random_2",
         ...
     }
}

And replace the hardcoded rules in the function with the data from the JSON file. How can I make something like this work ?

Upvotes: 0

Views: 152

Answers (3)

JRI
JRI

Reputation: 1932

As @ilkerkaran points out, you could use eval() to execute snippets of Javascript dynamically loaded from JSON, but that would introduce a large security risk into your code: those snippets could do anything!

It would be safer if you can constrain the structure of your JSON, to only allow certain types of test:

{
  "matchingRules": {
    "rule_1" : {
       "field_1": "Random_1",
       "field_2": "Random_1",
       "test": "=="
    },
    "rule_2" : {
       "field_1": "Random_2",
       "field_2": "Random_2",
       "test": ">"
    },
    ...
  }
}

While that would make your comparison function slightly more complicated to implement, it means that you can test whether field_1 and field_2 are actually valid properties of current and other, do any necessary conversion from string to other types, check their values are valid, and check whether test is a valid comparison for your application. Obviously you don't have to implement the test part if you're only interested in testing for equality.

Upvotes: 1

Nitheesh
Nitheesh

Reputation: 19986

Try using eval function

const matchingRules = {
  "rule_1": "other.Random_1 == current.Random_1",
  "rule_2": "other.Random_2 == current.Random_2",
}
const other = {
  Random_1: 10,
  Random_2: 20
}

const current = {
  Random_1: 10,
  Random_2: 200
}

console.log(eval(matchingRules.rule_1));
console.log(eval(matchingRules.rule_2));

Upvotes: 0

Amir Saleem
Amir Saleem

Reputation: 3140

You can use something like this

const identifiers = {
    "rules": {
        "Random_1": "Random_1",
        "Random_2": "Random_2",
    }
}

const comparer = (otherArray) => {
    return function (current) {
        return (
            otherArray.filter(function (other) {
                const entries = Object.entries(identifiers.rules);
                const conditions = entries.map((k, v) => (
                    k == v
                ));
                return conditions.indexOf(false) === -1;
            }).length == 0
        );
    };
};

Upvotes: 1

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