memoize.js

const memoizedGetSomeData = memoize(getSomeMoreData);
function getSomeData(foo, callback) {
    setTimeout(() => {
        callback('', foo + 1);
    },100)
}

function getSomeMoreData(foo, bar, callback) {
    setTimeout(() => {
        callback('', foo + bar + 1);
    },100)
}

getSomeData('a', (error, response) => {
  //slow
  getSomeData('a', (error2, response2) => {
    //slow
  })
})


// memoizedGetSomeData('a', (error, response) => {
//   //slow
//   console.log(response);
//   memoizedGetSomeData('a', (error2, response2) => {
//     //fast
//     console.log(response2);
//   })
// })
memoizedGetSomeData('a', {a:"b"}, (error, response) => {
  //slow
  console.log(response);
  memoizedGetSomeData('a', {a:"b"}, (error2, response2) => {
    //fast
    console.log(response2);
  })
})


function memoize(fn){
    var map = {};
    return function(){
        var args = [...arguments]
        var callB = args.pop();
        var arg = args.map(e => JSON.stringify(e)).join(":");
        console.log(arg);

        if(arg in map){
                console.log('cache hit');
                callB("", map[arg]);
        }else{
            var callBack = (err, out) => {
                map[arg] = out;
                callB(err, out);
            }
            fn.apply(this,[...args, callBack]);
        }
    }
}