The flat processing method of array

Arrays are frequently encountered in array operations, and we often need a single-layer array.

That is [1,2,[3,4,[5,[6,[7]]]] = = = [1, 2, 3, 4, 5, 6, 7], which we call the flat processing of the array.

Method One

If it's an array of pure numbers (you can also try a string), you can take advantage of the simple ToString and split methods

var arr = [1, ' A ', [3, ' 4 ', [' B ', [6,[7]]]]]console.log (arr.tostring ()]. Split (', '))//  [' 1 ', ' A ', ' 3 ', ' 4 ', ' B ', ' 6 ', ' 7 ']

Method Two

Using the recursive method, if the element or array continues to be called

var arr = [1, ' A ', [3, ' 4 ', [' B ', [6,[7] ]]; function Flatten (arr) {  = [];    for (Let i=0,len=arr.length;i<len;i++) {    if(Array.isarray (Arr[i])) {      = Res.concat (Flatten (arr[i));    } Else {      res.push (Arr[i])    }  }  return  res; Console.log (Flatten (arr))//[1, ' A ', 3, ' 4 ', ' B ', 6, 7]

The above code can be simplified by using the reduce method of the array

var arr = [[[1,[2]], ' a ', [3, ' 4 ', [' B ', [6,[7]]]]function  Flatten (arr) {    Return Arr.reduce ((prev,item) = {    return prev.concat (item)?  Flatten (item): item);  }, []);} Console.log (Flatten (arr))//[1, 2, ' A ', 3, ' 4 ', ' B ', 6, 7]

Both the reduce method and the Reduceright method iterate over all the items of an algebraic group and then build a final return value. The first method is a forward traversal, and the second is a backward traversal.

Accepts two parameters, the first is the function to be executed for each item, and the second is the initial value of the optional parameter as the base of the merge. The function receives 4 parameters: the previous value, the current value, the index of the item, and the array object.

Re-simplification

var arr = [[[1,[2]], ' a ', [3, ' 4 ', [' B ', [6,[7 = arr] = Arr.reduce ((a, b) = = A.concat (Array.isarray (b) ? Flat6 (b): b), []); Console.log (Flat6 (arr))//[1, 2, ' A ', 3, ' 4 ', ' B ', 6, 7]

Method Three

If it is determined that a simple two-tier nested array can use the extension operator provided by ES6

var arr = [[1,2],[3],[4,5,6]]console.log ([].concat (... arr.)]//[1, 2, 3, 4, 5, 6]

Find a better way to add it again ~ ~ ~

The flat processing method of array