1 将一个一维对象数组，根据相同的属性值，转化成一个二维数组
如
// 待转换的一维数组
var arrayFirst = [{
code: 1,
datas: 'a网吧'
},
{
code: 1,
datas: 'b网吧'
}, {
code: 2,
datas: 'a酒店'
},
{
code: 2,
datas: 'b酒店'
},
{
code: 3,
datas: 'a学校'
}, {
code: 3,
datas: 'b学校'
},
{
code: 3,
datas: 'c学校'
}
]
按照相同的code值转换成二维数组
// 转换后的二维数组
[
[{code: 1, datas: "a网吧"},{code: 1, datas: "b网吧"}],
[{code: 2, datas: "a酒店"},{code: 2, datas: "b酒店"}],
[{code: 3, datas: "a学校"},{code: 3, datas: "b学校"},{code: 3, datas: "c学校"}]]
————————————————
es6的方法
使用es6的方法
Object.values() //返回 值 数组
返回数组，成员是参数对象自身的（不含继承的）所有可遍历(enumerable)属性的键值
// 转换后的二维数组
var arrayTwo = Object.values(arrayFirst.reduce((res, item) => {
res[item.code] ? res[item.code].push(item) : res[item.code] = [item];
return res;
}, {}));
console.log(arrayTwo)
第二种方法
/ 转换后的二维数组
function convert (arr) {
var map1 = {};
while(arr.length) {
let current = arr.pop(); // 会影响原数组
map1[current.code] = map1[current.code] || [];
map1[current.code].push(current);
}
return Object.keys(map1).map(key => map1[key]);
}
var arrayTwo = convert(arrayFirst)
console.log(arrayTwo)
2 以上是一个具有相同code值的一维数组，需要转换成如下的二维数组
let arr = [
{code: "China", name: "xiaohuai"},
{code: "Africa", name: "neiLuoBi"},
{code: "Asia", name: "hanGuo"},
{code: "China", name: "tnnyang"},
{code: "Africa", name: "nanFei"},
{code: "China", name: "yangMan"}
]
var map = new Map();
var newArr = [];
arr.forEach(item => {
map.has(item.code) ? map.get(item.code).push(item) : map.set(item.code, [item]);
})
newArr = [...map.values()];
console.log(newArr);
实现了一维数组转二维，那么再将转换后的二维数组转换为一维数组呢？还是直接上代码吧：
let arr = [
[ {code: "China", name: "xiaohuai"}, {code: "China", name: "tnnyang"}, {code: "China", name: "yangMan"} ],
[ {code: "Africa", name: "neiLuoBi"}, {code: "Africa", name: "nanFei"} ],
[ {code: "Asia", name: "hanGuo"} ]
]
//方法一：
function reduceDimension(arr) {
var reduced = [];
for (var i = 0; i < arr.length; i++) {
for (var j = 0; j < arr[i].length; j++) {
reduced.push(arr[i][j]);
}
}
return reduced;
}
console.log(reduceDimension(arr));
//方法二：
console.log([].concat.apply([], arr));
