在Mongo中利用ES6默认参数

Question

I am wondering if there is a way I can construct mongo's queries to take advantage of es6 default parameters. I have the following method. I want to return all the data if make, model and year is not specified. I am trying to find an elegant solution but so far all I can think of is manual if else.

getStyles({ make = '', model = '', year = '-1' }) {
        return this.db
            .collection('styles')
            .find({ 'make.niceName': make, 'model.niceName': model, 'year.year': parseInt(year) })
            .toArray();
    }

Note: This is causing some confusion. I am using destructing on purpose. The problem is not how to write this function. The problem is how to construct a mongo query so it would ignore empty values.

Answer 1

Assuming getStyles is your own method, sure, you can give make , model , and year defaults. You can also give a default for the whole object you're destructuring so caller doesn't have to pass anything :

function getStyles({make = '', model = '', year = '-1'} = {}) {
// Overall default ------------------------------------^^^^^
    return // ...
}

The question is not how to organize/write my function but how to use es6 features to write a cleaner code that would work with mongo. IE if the user didn't pass anything I want to return all the styles but mongo actually looks for empty fields so it doesn't return anything.

It sounds to me like you don't want default parameters (except perhaps the overall default). Instead, you want to automate how you build the object you pass find .

Given your code example, you can readily do that with Object.keys on your object. So accept as an object, eg:

function getStyles(options = {}) {

...an then build your find options based on options :

const findParams = {};
Object.keys(options).forEach(key => {
  findParams[key + ".niceName"] = options[key];
});

Live example:

 function getStyles(options = {}) { const findParams = {}; Object.keys(options).forEach(key => { findParams[key + ".niceName"] = options[key]; }); console.log(`find options: ${JSON.stringify(findParams)}`); } let results = getStyles({make: "Ford", model: "Mustang"}); results = getStyles({make: "Ford", model: "Mustang", year: 2017}); 

If the mapping of the name you accept ( make ) to the name you need for find ( make.niceName ) isn't as easy as just appending .niceName , it's easy enough to have a Map (or just object) you build once:

const paramNames = new Map([
  ["make", "make.niceName"],
  ["model", "model.niceName"],
  ["year", "year.niceName"]
]);

...and then use:

const findParams = {};
Object.keys(options).forEach(key => {
  const paramName = paramNames.get(key);
  if (paramName) {
    findParams[paramName] = options[key];
  }
});

Live example:

 const paramNames = new Map([ ["make", "make.niceName"], ["model", "model.niceName"], ["year", "year.niceName"] ]); function getStyles(options = {}) { const findParams = {}; Object.keys(options).forEach(key => { const paramName = paramNames.get(key); if (paramName) { findParams[paramName] = options[key]; } }); console.log(`find options: ${JSON.stringify(findParams)}`); } let results = getStyles({make: "Ford", model: "Mustang"}); results = getStyles({make: "Ford", model: "Mustang", year: 2017}); 

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Side note: Defaults don't have to be strings, so if you use numbers for year rather than strings, your default would just be -1 , not '-1' .