Q: How do you flat an Array?

Question

Sigiloso · Accepted Answer

[[1],[[2],[3]]].reduce((acc, curr) => {
return acc.concat(Array.prototype.concat.apply([],curr));
}, [])

Sigiloso · Answer

// Method 1
const flattenArr = (arr) => {
    if(arr instanceof Array && arr.length === 0)
        return [];
    else if(!(arr instanceof Array))
        return [arr];
    return flattenArr(arr[0]).concat(flattenArr(arr.slice(1)));
}

// Method 2
const flattenArr = (arr) => {
    const result = [];
    const helper = (arr) => {
        if(Number.isInteger(arr)) {
            result.push(arr);
        } else if (Array.isArray(arr)) {
            for(let i = 0; i < arr.length; i++) {
                helper(arr[i]);
            }
        }
    }
    helper(arr);
    return result;
}

Sigiloso · Answer

var flattenArray = [].prototype.concate.apply([], UnflattenArray)
OR
function flatten(arr) {
    return arr.reduce(function (flat, toFlatten) {
        return flat.concat(Array.isArray(toFlatten) ? flatten(toFlatten) : toFlatten);
    }, []);
}

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