如何从元素数量由 Object.values 确定的对象生成数组？

Question

I have an object like so:

{ green: 2, blue: 1, red: 2}

How can I turn it into an array that looks like this:

[ 'green', 'green', 'blue', 'red', 'red']

Answer 1

Could be done like this:

Object.entries(obj).flatMap(([k, v]) => Array(v).fill(k));

Example:

 const obj = { green: 2, blue: 1, red: 2}; const res = Object.entries(obj).flatMap(([k, v]) => Array(v).fill(k)); console.log(res);

Answer 2

This is a neat way with a generator. Perhaps a little overkill for this example.

 function* makeIterator(obj) { const keys = Object.keys(obj); for (const key of keys) { const value = obj[key]; for (let i = 0; i < value; i++) { yield key; } } } const obj = {green: 2, blue: 1, red: 2}; console.log(Array.from(makeIterator(obj)));

Answer 3

Use reduce with Object.entries :

 const obj = { green: 2, blue: 1, red: 2}; const res = Object.entries(obj).reduce((a, [k, v]) => (a.push(...new Array(v).fill(k)), a), []); console.log(res);

Answer 4

Object.entries will do that - it gives a key: value pair of each property in the object. You then use the value to push the key into an array that gives you the desired output.

 var obj = { green: 2, blue: 1, red: 2}; var newArr = []; var objEntries = Object.entries(obj); objEntries.forEach(function(item){ for(var i = 0; i < item[1]; i++){ newArr.push(item[0]) }; }) console.log(newArr); // gives //[ 'green', 'green', 'blue', 'red', 'red']

Answer 5

var data={ green: 2, blue: 1, red: 2};
var newData=[];
for(let i in data){
    for(let j=0;j<data[i];j++){
        newData.push(i);
    }
}
console.log('newData = ', newData);

output

newData = ["green", "green", "blue", "red", "red"]

Answer 6

In the case you do not want to deal with polifills for flatMap support in IE etc you can also consider this solution which is based only on Object.keys and Array.forEach :

 let obj = {green: 2, blue: 1, red: 2}, arr=[] Object.keys(obj).forEach(x => arr.push(...Array(obj[x]).fill(x))) console.log(arr)

Another approach you can take to avoid ES6 Array destructuring is via Array.reduce and Object.entries :

 let obj = {green: 2, blue: 1, red: 2} let r = Object.entries(obj).reduce((r,[k,v]) => r.concat(Array(v).fill(k)),[]) console.log(r)

Answer 7

Using map and flat if you don't want to use flatMap directly

const obj = { 
   green: 2, 
   blue: 1, 
   red: 2
};

const responseArray = Object.entries(obj)
    .map(([key,value]) => {
        return Array(value).fill(key)
}).flat();

console.log(responseArray);
//  ["green", "green", "blue", "red", "red"]