數組的扁平化,就是將一個嵌套層的數組轉換爲只有一層的數組
例如:
var arr = [1,2,3,[4,5,66],[4343,[22,3,4,5,[2,'ggg',['dd','aa',['qqq','www','eee'],'zzz']]],55353,[1,2,34,6,7],55]];
下面是扁平化的數據
var ans = [1, 2, 3, 4, 5, 66, 4343, 22, 3, 4, 5, 2, "ggg", "dd", "aa", "qqq", "www", "eee", "zzz", 55353, 1, 2, 34, 6, 7, 55];
實現方法
寫法一(遞歸遍歷)
function isArray(obj){
return Object.prototype.toString.call(obj) == '[object Array]';
}
function flatten(arr){
var arr = arr || [],
resArr = [],
len = arr.length;
for(var i = 0; i < len; i++){
if(isArray(arr[i])){
resArr = resArr.concat(flatten(arr[i]));
}else{
resArr.push(arr[i]);
}
}
return resArr;
}
寫法二(原型鏈上寫)
Array.prototype.flatten = function (){
var resArr = [];
this.forEach(function (item){
Object.prototype.toString.call(item) == '[object Array]' ? resArr = resArr.concat(item.flatten()) : resArr.push(item);
})
return resArr;
}
寫法三(reduce)
function flatten1(arr){
var res = arr || [];
return res.reduce(function(prev,next){
return Object.prototype.toString.call(next) == '[object Array]' ? prev.concat(flatten1(next)) : prev.concat(next);
},[])
}
寫法四(ES6.0)
const flatten2 = arr => arr.reduce((prev,next) => Object.prototype.toString.call(next) == '[object Array]' ? prev.concat(flatten1(next)) : prev.concat(next),[]);