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Use the reduce method in combination with the concat method to “flatten” an array of arrays into a single array that has all the elements of the original arrays.
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| // Use the reduce method in combination with the concat method to | |
| // “flatten” an array of arrays into a single array that has all | |
| // the elements of the original arrays. | |
| // My original "solution": | |
| let arrays = [[1, 2, 3], [4, 5], [6]]; | |
| arrays.reduce((accumulator, currentValue) => accumulator.concat(currentValue),[]); // [1, 2, 3, 4, 5, 6] | |
| // This solution works on the sole test case in Chapter 5 of Eloquent JavaScript; but it doesn't work with nested arrays. | |
| // For instance: | |
| // [[1], [1,[1,2]], [3,[4,[5,6]]]].reduce((accumulator, currentValue) => accumulator.concat(currentValue),[]); | |
| // will return: | |
| // [1, 1,[1, 2], 3, [4,[5, 6]] 🙁 | |
| // Jem Young provides this alternate solution in in FrontEndMasters course. The solution above works with the caveat | |
| // that it cannot handle nested arrays - it will work on an array of arrays that only contain primitives (or arrays of | |
| // primitives and arrays that only contain primitives) . It will not work on arrays of arrays of arrays. Introducing | |
| // recursive concatenation resolves this problem by flattening the nested arrays. | |
| function flatten(arr) { | |
| return arr.reduce((acc, item) => { | |
| if (Array.isArray(item)) { | |
| acc = acc.concat(flatten(item)); | |
| } else { | |
| acc.push(item); | |
| } | |
| return acc; | |
| }, []); | |
| } |
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