将具有相同值的对象键分组
我有一个对象
var myObject = {"audi": "gas", "tesla": "electric", "bmw": "electric", "mercedes": "electric"}
我想将所有具有相同值的键分组在一个字符串中，就像只使用 es5
tesla bmw mercedes: electric. audi: gas
我使用了Object.keys和的组合，Object.values但对我不起作用
var res = ''
Object.keys(myObject).map(function(key) {
Object.values(myObject).map(function(val) {
if (myObject[key] === val) {
kes = {
[res.concat(key)]: val
}
}
})
})
回答
按“燃料”分组更有意义。为此，您可以使用reducer。
在片段中，通往罗马的几条不同道路......
也可以看看...
const logElem = document.querySelector(`pre`);
var myObject = {
audi: "gas",
tesla: "electric",
bmw: "electric",
mercedes: "electric"
};
const byFuel = Object.entries(myObject)
.reduce((acc, [key, value]) =>
({ ...acc, [value]: (acc[value] || []).concat(key) }), {});
logElem.textContent = `***By fuel (ES6)***\n ${
JSON.stringify(byFuel, null, 2)}`;
// to swap keys and values from [byFuel]
const byCars = Object.entries(byFuel)
.reduce((acc, [key, value]) => ({ ...acc,
[value.join(`,`)]: key
}), {});
logElem.textContent += `\n\n***By cars from byFuel (ES6)***\n${
JSON.stringify(byCars, null, 2)}`;
// Use one reducer (ES6)
const byCarsInOne = Object.entries(myObject)
.reduce((acc, [key, value]) => {
const keysAggregatedAsSingleKey = Object.keys(myObject)
.filter( key => myObject[key] === value )
.join(`,`);
return acc[keysAggregatedAsSingleKey]
? acc
: { ...acc, [keysAggregatedAsSingleKey]: value };
}, {});
logElem.textContent += `\n\n***One reducer***\n${
JSON.stringify(byCarsInOne, null, 2)}`;
// ES5 (really necessary? All modern browsers support es6)
var byFuelEs5 = {};
var byCarsEs5 = {};
for (var key in myObject) {
var ky = myObject[key];
byFuelEs5[ky] = ky in byFuelEs5
? byFuelEs5[ky].concat(key)
: [key];
}
logElem.textContent += `\n\n***ES5***\n${
JSON.stringify(byFuelEs5, null, 2)}`;
for (var key in byFuelEs5) {
byCarsEs5[byFuelEs5[key].join(`,`)] = key;
}
logElem.textContent += `\n\n${
JSON.stringify(byCarsEs5, null, 2)}`;
// Object.keys ES5, not very efficient
// (makes you *really* want to use ES6 ;)
var cars = Object.keys(myObject);
var byCarsEs5_2 = cars
.map( function(key) {return [myObject[key], key]; })
.map( function(kv) {
var fuel = kv[0];
var comma = this[fuel] ? "," : "";
this[fuel] = (this[fuel] || "") + comma + kv[1];
return this; }, {} )
.map( function(obj) {
var keys = Object.keys(obj)
.map( key => this[obj[key]] = key );
return this;
}, {}).shift();
logElem.textContent += `\n\n***Object.keys and map ES5***\n${
JSON.stringify(byCarsEs5_2, null, 2)}`;
// Finally, reduce from Object.keys my be more efficient
var byCarsEs5_3 = cars
.reduce( function(acc, car) {
var fuel = myObject[car];
if (!~acc.fuels.indexOf(fuel)) {
acc.fuels.push(fuel);
var carsByFuel = cars.filter(key => myObject[key] === fuel);
acc.result[carsByFuel] = fuel;
}
return acc;
}, {fuels: [], result: {}} ).result;
logElem.textContent += `\n\n***ES5 one reducer from Object.keys***\n${
JSON.stringify(byCarsEs5_3, null, 2)}`;<pre></pre>