如下圖康辑，在一維數(shù)組中若將含有相同字段屬性的歸納，轉(zhuǎn)換為二維數(shù)組
- 一維數(shù)組
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"}
]
- 二維數(shù)組
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"} ]
]
1. 將一維數(shù)組轉(zhuǎn)換成二維數(shù)組
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"}
]
// 重點
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);
2. 將二維數(shù)組轉(zhuǎn)換成一維數(shù)組
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));
方法一是循環(huán)遍歷，沒啥說的。方法二有必要說一下，apply方法會調(diào)用一個函數(shù)元潘，apply方法的第一個參數(shù)會作為被調(diào)用函數(shù)的this值，apply方法的第二個參數(shù)（一個數(shù)組君仆，或類數(shù)組的對象）會作為被調(diào)用對象的arguments值翩概，也就是說該數(shù)組的各個元素將會依次成為被調(diào)用函數(shù)的各個參數(shù)
