I have a nested/multi-dimensional array like so:
[ [ 1, 1, a ], [ 1, 1 , b ], [ 2, 2, c ], [ 1 ,1, d ] ]
And I want to filter it so that it returns only unique values of the outer array based on the 1st value of each nested array.
So from the above array, it would return:
[ [1,1,a] [2,2,c] ]
Am trying to do this in vanilla javascript if possible. Thanks for any input! =)
Here is my solution.
const dedup = arr.filter((item, idx) => arr.findIndex(x => x[0] == item[0]) == idx)
It looks simple and also somehow tricky a bit.
I realize there's already three solutions, but I don't like them. My solution is
So here it is:
/**
* @param arr - The array to get the unique values of
* @param uniqueBy - Takes the value and selects a criterion by which unique values should be taken
*
* @returns A new array containing the original values
*
* @example unique(["hello", "hElLo", "friend"], s => s.toLowerCase()) // ["hello", "friend"]
*/
function unique(arr, uniqueBy) {
const temp = new Set()
return arr.filter(v => {
const computed = uniqueBy(v)
const isContained = temp.has(computed)
temp.add(computed)
return !isContained
})
}
const arr = [ [ 1, 1, 'a' ], [ 1, 1, 'b' ], [ 2, 2, 'c' ], [ 1, 1, 'd' ] ]
console.log(unique(arr, v => v[0]))You could filter with a set and given index.
const
uniqueByIndex = (i, s = new Set) => array => !s.has(array[i]) && s.add(array[i]),
data = [[1, 1, 'a'], [1, 1, 'b'], [2, 2, 'c'], [1, 1, 'd']],
result = data.filter(uniqueByIndex(0));
console.log(result);
const input = [[1,1,'a'], [1,1,'b'], [2,2,'c'], [1,1,'d']]
const res = input.reduce((acc, e) => acc.find(x => x[0] === e[0])
? acc
: [...acc, e], [])
console.log(res)Create the object with keys as first element of array. Iterate over array, check if the first element of array exist in the Object, if not push into the array.
const nestedArr = [ [1,1,"a"], [1,1,"b"], [2,2,"c"], [1,1,"d"] ];
const output = {};
for(let arr of nestedArr) {
if(!output[arr[0]]) {
output[arr[0]] = arr;
}
}
console.log(Object.values(output));Another solution, would be to maintain the count of first array element and if the count is equal to 1, then push in the final array.
const input = [ [1,1,"a"], [1,1,"b"], [2,2,"c"], [1,1,"d"] ],
count = {},
output = [];
input.forEach(arr => {
count[arr[0]] = (count[arr[0]] || 0) + 1;
if(count[arr[0]] === 1) {
output.push(arr);
}
})
console.log(output);