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Flatten Array ES6
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| /** | |
| * Flattens deeply nested array into simple array | |
| * @param {Array} arr - input array of numbers | |
| * @param {Array} [acc] - accumulator to store resulting array during recursion calls | |
| * @return {Array} | |
| */ | |
| const flatten = (arr, acc = []) => { | |
| const isArray = Array.isArray(arr); | |
| // safe check for input | |
| if (!isArray) return arr; | |
| // Returns accumulator when there is no input items | |
| if (isArray && !arr.length) return acc; | |
| // get head and tail of input array | |
| const head = arr[0]; | |
| const tail = arr.slice(1); | |
| // recursion call when input item is an array | |
| if (Array.isArray(head)) { | |
| return flatten(head.concat(tail), acc); | |
| } | |
| // store head into accumulator and process tail recursively | |
| return flatten(tail, acc.concat(head)); | |
| } | |
| console.log(flatten([[1,2,[3]],4])); |
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