JS Promise.all

data(){
    return {
        list: [1, 2, 3]
    }
},
created(){
    let arr = [];
    this.list.map(item => {
        arr.push(this.getClassify(item))
    });
    let promise = Promise.all(arr).then(res => {
        console.log("Promise.all", res, res.length);
    });             
},
methods:{
    getClassify(item) {
        return new Promise((resolve, reject) => {
            resolve(item * item);
        });
    },
}