JS method of changing two-dimensional array to one-dimensional array

Method 1 ：

utilize es5 Of reduce Realization .

var arr1 = [[0, 1], [2, 3], [4, 5]];
var arr2 = arr1.reduce(function (a, b) {
     
    return a.concat(b)
});

Method 2 ：

adopt Array.isArray Determine whether it is a multidimensional array , If it is , Do recursive operations .

var arr1 = [[1,2],3,[[[4], 5]]];
function flatten(arr) {
     
    return [].concat( ...arr.map(x => 
        Array.isArray(x) ? flatten(x) : x
    ))
}
var arr2 = flatten(arr1); 

Method 3 ：

utilize apply Realization .

var arr1 = [[0, 1], [2, 3], [4, 5]];
var arr2 = [].concat.apply([], arr1); //  perhaps  Array.prototype.concat.apply([], arr1);