前端理论总结（js）——reduce相关应用方法

按属性对object分类

let peple=[
    {name:'Alice',age:21},
    {name: 'Mex', age: 20},
    {name:'Jane',age:20}
}

function groupBy (objectArray, property) {
    return objectArray.reduce(function(pre, cur){
        let key=cur[property]
        if(!pre[key]){
            pre[key]=[]
        }
        pre[key].push(cur)
        return pre

    },{})
}
let groupByPeople-groupBy(peple, 'age')

console. log(groupByPeople)
/**{
'20': [ { name: 'Mex', age: 20 }, { name: 'Jane', age: 20 } ],
'21': [ { name: 'Alice', age: 21 } ]
}*/

使用扩展运算符和initialValue绑定包含在对象数组中的数组

let friends = [{
    name: 'Anna',
    books: ['Bible', 'Harry Potter'],
    age: 21
},{
    name: 'Bob',
    books: ['War and peace', 'Romeo and Juliet'],
    age: 26
},{
    name: 'Alice',
    books: ['The Lord of the Rings', 'The Shining'],
    age: 18
}]

let allbook=friends.reduce((pre,cur) ->{
    let key=cur['books']
    return [ ... pre, ... key]

},['alphoter'])
console.log(allbook);

/**
[
'alphoter',
'Bible',
'Harry Potter',
'War and peace',
'Romeo and Juliet',
'The Lord of the Rings',
'The Shining
]
*/

ヾ(￣▽￣)Bye~Bye~