From an object like this:
{a:1, b: 2, c: 3}
I would like to turn into
['a', 'b', 'b', 'c', 'c', 'c']
Where the key is the string and the value is the number of copies, order doesn't matter.
What's the best way to do this?
I was thinking about using array.fill but not sure if that's actually easier than just iterating and push.
Edit: Currently this:
const arr = []
_.each(obj, function (v, k) {
_.times(v, function () {
arr.push(k)
})
})
You could flatMap the Object.entries and fill an array of each size.
const obj = { a: 1, b: 2, c: 3 };
const result = Object.entries(obj).flatMap(([k, v]) => Array(v).fill(k));
console.log(result)or with Lodash
const obj = { a: 1, b: 2, c: 3 };
const arr = _.flatMap(obj, (v,k) => Array(v).fill(k))
console.log(arr);<script src="https://cdn.jsdelivr.net/npm/lodash@4.17.21/lodash.min.js"></script>But there's nothing like a simple loop
const obj = { a: 1, b: 2, c: 3 };
const result = []
for (let [k, v] of Object.entries(obj)) {
while (v--) {
result.push(k)
}
}
console.log(result)You can use Object.entries and Array#reduce as follows:
const input = {a:1, b: 2, c: 3};
const output = Object.entries(input).reduce(
(prev, [key,value]) => prev.concat( Array(value).fill(key) ),
[]
);
console.log( output );Or, using Array#push instead of Array#concat,
const input = {a:1, b: 2, c: 3};
const output = Object.entries(input).reduce(
(prev, [key,value]) => prev.push( ...Array(value).fill(key) ) && prev,
[]
);
console.log( output );Or, using for loops,
const input = {a:1, b: 2, c: 3};
const output = [],
pairs = Object.entries(input);
for(let i = 0; i < pairs.length; i++) {
const [key, value] = pairs[i];
for(let j = 0; j < value; j++) {
output.push( key );
}
}
console.log( output );I would convert the object into an array of keys using Object.keys and then use a newly created empty results array, then map through the keys.
For each key I would add a fill array to the existing results.
Here's the ES6 solution to that (no extra libraries required)
const obj = { a: 1, b: 2, c: 3 };
let result = []
Object.keys(obj).forEach(key => {
result = [...result, ...new Array(obj[key]).fill(key)]
})
console.log(result)