Is there any way of chaining queries dynamically?

For example, given the following GET request

/collection?field1=value1&field2=value2&sort=field3 asc

It is easy without the sort query

/collection?field1=value1&field2=value2

var query = {}
for (var key in query) {
    query[key] = req.query[key]
}

Collection.find(query)

But how do I build the GET request if there are optional query keys such as sort, expand, and select which map to Collection.sort, Collection.populate, Collection.select respectively?

In other words, suppose you have a dynamic array of Query methods:

queries = [populate, select, sort]

Would the solution be the following:

var query = Collection.find()
for (var q in queries)
    query = query.q

CodePudding user response：

You just iterate through the query parameters and separate out the ones that are operations versus actual query criteria. Using your examples:

// sample data for req.query
const req = {
  query: {
    sort: "field9",
    field1: "someValue",
    field2: "otherValue",
    field3: "highValue"
  }
};

const queries = new Map();
const operations = new Map([
    ["populate", false], 
    ["sort", false], 
    ["select", false]
]);
for (const [key, value] of Object.entries(req.query)) {
    if (operations.has(key)) {
        operations.set(key, value);
    } else {
        queries.set(key, value);
    }
}

// here:
//    queries contain the non-operation pairs
//    operations (if not false) contain the operation value such
//      as sort => "field9"

console.log("operations:");
for (let [key, value] of operations.entries()) {
   console.log(`${key} => ${value}`);
}
console.log("queries:");
for (let [key, value] of queries.entries()) {
   console.log(`${key} => ${value}`);
}

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To run the operation, you'd then have to check which operations are present and branch your code and query based on which operations are present.