JavaScript how to call a function's function etc.. based off an array?

Question

I'm really not sure how to word this question, which is why I've had some trouble googling it, but I'm trying to make, basically, a helper function for modifying mongoDB data, and I have a list of commands, in this format:

              var commands = {
                    "find": {
                        "names": {
                            "find":["query"],
                            "toArray":["callback"]
                        }
                    },
                    "sort": {
                        "names": {
                            "find":[],
                            "sort":["query"],
                            "toArray":["callback"]
                          }                          
                    },
                    "limit": {
                        "names": {
                            "find":[],
                            "limit":["number"],
                            "toArray":["callback"]
                          }                          
                    },
                    "deleteOne": {
                        "args":["query","callback"]
                    },
                    "findOne": {
                        "args":["query", "callback"]
                    },
                    "insertOne": {
                        "args":["query", "callback"]
                    },
                    "insertMany": {
                        "args":["array"]
                    },
                    "remove": {
                        "args":["query", "callback"]
                    },
                    "drop": {
                        "args":["callback"]
                    },
                    "updateOne": {
                        "args":["query", "newvalues", "callback"]
                    },
                    "aggregate": {
                        "args": ["query"],
                        "hasCB":"toArray"
                    },
                    "createCollection": {
                        "args":["string", "callback"]
                    }
                };

and then a dictionary of those values: and the idea is to call a particular mongoDB function based on the input, like

Based off of this, I am able to make an array that looks like this:

[["find",[]],["sort",[{"name":-1}]],["toArray",[/*some function reference*/]]],

and based on that, I want to call:

something.find().sort({"name":-1}).toArray(callback);

and if I have something like this:

[["find",[{"name":"hi"}]],["toArray",[/some function reference/]]],

I should be able to produce the result of: something.find({"name":"hi"}).toArray(cb);

all in the same function.

This isn't EXACTLY a node.js question, more of JavaScript in general, that given a function in the format of

[[functionName1,arrayOfArguments1],[functionName2,arrayOfArguments2],[functionName3,arrayOfArguments3]]

how do you call functionName1(...arrayOfArguments1)[functionName2](...arrayOfArguments2)[functionName3](...arrayOfArguments3),

using a loop, or one function ,lets say? Instead of manually writing it out, how do I produce this result? I'm currently doing it like this with a switch / case, but that's less than ideal:

switch(funcList.length) {
                        case 2:
                            console.log(col[funcList[0][0]](...funcList[0][1])[funcList[1][0]](...funcList[1][1]));
                            break;
                        case 3:
                            console.log(col[funcList[0][0]](...funcList[0][1])[funcList[1][0]](...funcList[1][1])[funcList[2][0]](...funcList[2][1]));
                            break;
                    }

Why is the nested data structure necessary? `["find","names","find","query","toArray", "callback"]` or `"find names find query toArray callback"` produce the same result. — guest271314, Feb 06 '19 at 05:26
See [Execute Promise tree consecutively from parent to child](https://stackoverflow.com/q/54083642/) — guest271314, Feb 06 '19 at 05:43

score 0 · Answer 1 · answered Feb 06 '19 at 05:06

0

You Just parse with Table Name

var Jstr = JSON.parse(commands).find;

Now, Jstr Contains

"names": {
     "find":["query"],
      "toArray":["callback"]
  }

Like this same, you can parse and get the value.

answered Feb 06 '19 at 05:06

Elango Sengottaiyan

166
1
2
13

Hi thanks, I'm able to get the values fine, the problem is turning those values into a function call for the sub-functions. Each object in the array represents a different function call, so [["find",["query"]],["toArray", ["callback"]]] would result to: masterFunction["find"]("query")["toArray"]["callback"], see where I'm going with this? :) – B''H Bi'ezras -- Boruch Hashem Feb 06 '19 at 07:13

score 0 · Answer 2 · answered Feb 06 '19 at 05:11

0

Let's say

const functionArr = [["find",[]],["sort",[{"name":-1}]],["toArray",[/*some function reference*/]]];

you can then write,

const functionChainResult = initialObj;
functionArr.forEach(fn => {
  functionChainResult = functionChainResult.apply(window[fn[0]], fn[1]);
});
console.log(functionChainResult);

For using some context other than window, you can see this.

answered Feb 06 '19 at 05:11

Aakash Verma

3,705
5
29
66

Hi thanks, but I think I'm mis-explaining myself: I'm not simply trying to call an array of functions with their argument pairs, I can do that easily with arr.forEach(x=>functionDictionary(x[0])(...x[1]), the problem is that I'm trying to call SUB functions in a recursive manner, like lets say an object has a function: foo(arg).bar(other).foobar(int, str).execute(str), so each element of the array represents a different SUB function: [["foo",["asdf"]],["bar",["other"]],["foobar",[123,"hi"]],["execute",["today"]]] ??? How do I produce the function call from the array?? – B''H Bi'ezras -- Boruch Hashem Feb 06 '19 at 07:00

score 0 · Answer 3 · answered Feb 06 '19 at 05:43

What I understand from your question is you want to call some sequence of functions based on an array which had set of the function name in strings. If I am right, I think this solution will help you.
Let's try to use 'apply' feature in a function.


var arrx = [["find",[]],["sort",[{"name":-1}]],["toArray",[x]]];

function callSequence(model, operationArray) {
  var res = model; // this will help to call function chain

  // recursive function
  function call(arr, index) {
    // arr[index][0] is current function name
    // arr[index][1] is current function arguments 
    res = res[arr[index][0]].apply({}, arr[index][1]);
    if(index < arr.length) {
      call(arr, index + 1); // call recursively throught the array.
    }
  }

  call(arrx, 0);
}

callSequence(Something, arrx);

Hi thanks for the detailed code answer, but I'm actually not trying to simply call a sequence of individual functions; rather, each element in the array represents a different sub-function, so for example, this array: [["find",["query"]],["toArray", ["callback"]]] should produce this result: masterFunction["find"]("query")["toArray"]["callback"], I'm able to call the functions IF they were their own functions, simply with: arr.forEach(x=>functionDictionary(x[0])(...x[1]) — B''H Bi'ezras -- Boruch Hashem, Feb 06 '19 at 07:15

JavaScript how to call a function's function etc.. based off an array?

3 Answers3