正确插入键值对javascript

Question

I am working to fix some legacy code. I have made an example and the results will follow. This is an example of the old array.

var old = { 1: ['A', 'E', 'I', 'O', 'U'] };

This should be what is returned

var expected = { a: 1, e: 1, i: 1, o: 1, u: 1 };

Now if I use this

var ETL = function(){};

ETL.prototype.transform = function(old){
    var array = [];
    for (var variable in old) {
        console.log(variable);
        for(var i = 0; i < old[variable].length; i++){
            var obj = {};
            var key = old[variable][i].toLowerCase();
            obj[key] = parseInt(variable);
            array.push(obj);
        }
    }
    return array;
};

I get this result

[ { a : 1 }, { e : 1 }, { i : 1 }, { o : 1 }, { u : 1 } ]

Which is really close but not quite what I'm looking for. I think I've created an array of objects when I really just want an object with key value pairs. I think step 1 is to redeclare array as an object, and then step 2 is to rework the code to work with an object instead of an array. I'm just not exactly sure how to do that.

Answer 1

var obj = {};
for(var i = 0; i < old[variable].length; i++){

            var key = old[variable][i].toLowerCase();
            obj[key] = parseInt(variable);
            //array.push(obj);
        }

Declare obj only once. You are creating it in every iteration of loop

Answer 2

You can use array reduce method to resolve it.

var old = { 1: ['A', 'E', 'I', 'O', 'U'] };
var _getOne = old['1']; //get value of key 1

function getWordCnt(arr){
    return arr.reduce(function(prev,next){
        prev[next] = (prev[next] + 1) || 1;
        return prev;
    },{});
}
console.log(getWordCnt(_getOne))

Check this jsfiddle

Note : Better to have a key as a string instead of an integer

Answer 3

Assuming that your have many properties of the object each with an array of capital letters the following single line assignment will turn them all into the new form.

 var old = { 1: ['A', 'E', 'I', 'O', 'U'], 2: ['B', 'T', 'O', 'M', 'V'], 3: ['C', 'B', 'X', 'N', 'S'] }, newList = Object.keys(old).map(k => old[k].reduce((p,c) => {p[c.toLowerCase()] = k*1; return p},{})); document.write("<pre>" + JSON.stringify(newList,null,2) + "</pre>");