for循环中的异步获取的问题

我有如下的示例代码,但是resolve后得到是空,因为在for中使用了多个异步获取的函数,导致了最终获得的结果只有1条,各位大神出来帮忙给点意见,主要目的是学习Promise

var arr1= [
        {id:1,name:'Jason', age: 23, content:'我是来学习的家伙'},
        {id:2,name:'Jason2', age: 23, content:'我是来学习的家伙'},
        {id:3,name:'Jason3', age: 23, content:'我是来学习的家伙'},
        {id:4,name:'Jason4', age: 23, content:'我是来学习的家伙'},
        {id:5,name:'Jason5', age: 23, content:'我是来学习的家伙'},
        {id:6,name:'Jason6', age: 23, content:'我是来学习的家伙'},
        {id:7,name:'Jason7', age: 23, content:'我是来学习的家伙'},
        {id:8,name:'Jason8', age: 23, content:'我是来学习的家伙'},
        {id:9,name:'Jason9', age: 23, content:'我是来学习的家伙'},
        {id:10,name:'Jason11', age: 23, content:'我是来学习的家伙'},
        {id:11,name:'Jason12', age: 23, content:'我是来学习的家伙'},
        {id:12,name:'Jason13', age: 23, content:'我是来学习的家伙'},
        {id:13,name:'Jason14', age: 23, content:'我是来学习的家伙'},
        {id:14,name:'Jason15', age: 23, content:'我是来学习的家伙'},
        {id:15,name:'Jason16', age: 23, content:'我是来学习的家伙'},
        {id:16,name:'Jason17', age: 23, content:'我是来学习的家伙'},
        {id:17,name:'Jason18', age: 23, content:'我是来学习的家伙'},
        {id:18,name:'Jason19', age: 23, content:'我是来学习的家伙'},
        {id:19,name:'Jason22', age: 23, content:'我是来学习的家伙'},
        {id:20,name:'Jason23', age: 23, content:'我是来学习的家伙'},
        {id:21,name:'Jason24', age: 23, content:'我是来学习的家伙'},
        {id:22,name:'Jason25', age: 23, content:'我是来学习的家伙'},
        {id:23,name:'Jason26', age: 23, content:'我是来学习的家伙'},
        {id:24,name:'Jason27', age: 23, content:'我是来学习的家伙'},
        {id:25,name:'Jason28', age: 23, content:'我是来学习的家伙'},
        {id:26,name:'Jason29', age: 23, content:'我是来学习的家伙'},
        {id:27,name:'Jason33', age: 23, content:'我是来学习的家伙'},
        {id:28,name:'Jason34', age: 23, content:'我是来学习的家伙'},
        {id:29,name:'Jason35', age: 23, content:'我是来学习的家伙'},
        {id:30,name:'Jason36', age: 23, content:'我是来学习的家伙'},
        {id:31,name:'Jason37', age: 23, content:'我是来学习的家伙'},
        {id:32,name:'Jason38', age: 23, content:'我是来学习的家伙'},
        {id:34,name:'Jason39', age: 23, content:'我是来学习的家伙'},
        {id:35,name:'Jason44', age: 23, content:'我是来学习的家伙'},
        {id:36,name:'Jason41', age: 23, content:'我是来学习的家伙'},
        {id:37,name:'Jason42', age: 23, content:'我是来学习的家伙'},
        {id:38,name:'Jason43', age: 23, content:'我是来学习的家伙'}
    ]
    var arr2 = [
        {class:'一年级2班', userId: 33},
        {class:'一年级3班', userId: 3},
        {class:'一年级2班', userId: 5},
        {class:'一年级6班', userId: 38},
        {class:'一年级2班', userId: 21},
        {class:'一年级3班', userId: 2},
        {class:'一年级2班', userId: 1},
        {class:'一年级9班', userId: 5},
        {class:'一年级2班', userId: 7},
        {class:'一年级1班', userId: 10},
        {class:'一年级2班', userId: 13},
        {class:'一年级5班', userId: 23}
    ]
    var arr3 = [
        {scope:80, userId: 21},
        {scope:50, userId: 5},
        {scope:70, userId: 10},
        {scope:20, userId: 23},
        {scope:70, userId: 13},
        {scope:44, userId: 3},
        {scope:23, userId: 33},
        {scope:76, userId: 1},
        {scope:45, userId: 10},
        {scope:26, userId: 38},
        {scope:65, userId: 7},
        {scope:45, userId: 30},
        {scope:76, userId: 22},
        {scope:46, userId: 4},
        {scope:95, userId: 8},
        {scope:100, userId: 9},
        {scope:74, userId: 35}
    ]
   //获取所以学生的名字和ID
   function getName() {
        return new Promise((resolve, reject) => {
            let cf = []
            arr1.map(item => {
                cf.push({id: item.id,name:item.name})
            })
            resolve(cf)    
        })
    }
    //获取学生的分数
    function getScope(id) {
        return new Promise((resolve,reject) => {
            arr3.map(item=>{
                if(id == item.userId){
                    resolve(item.scope)
                }
            })
            
        })
    }
    function allPromise() {
    return new Promise((resolve, reject) => {
        let data = []
        getName().then(res => {
            console.log('res', res)
            let promise1 = []
            for (var i = 0; i < res.length; i++) {

                let name = res[i].name
                let id = res[i].id
                let classes, scope
                for (var j = 0; j < arr2.length; j++) {
                    if (arr2[j].userId == id) {
                        classes = arr2[j].class
                        getScope(id).then(result => {
                            scope = result
                            data.push({
                                id: id,
                                name: name,
                                class: classes,
                                scope: scope
                            })
                        })
                    }
                }
            }
        })
        console.log(data)
        resolve(data)
    })
}
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2 个回答

这里可以考虑用 Promise.all,看起来你是想批量取出来然后统一处理。

已经解决,原来是resolve放错了位置,感谢大家的关注,如下:

function allPromise() {
    return new Promise((resolve, reject) => {
        let data = []
        getName().then(res => {
            console.log('res', res)
            let promise1 = []
            for (var i = 0; i < res.length; i++) {

                let name = res[i].name
                let id = res[i].id
                let classes, scope
                for (var j = 0; j < arr2.length; j++) {
                    if (arr2[j].userId == id) {
                        classes = arr2[j].class
                        getScope(id).then(result => {
                            scope = result
                            data.push({
                                id: id,
                                name: name,
                                class: classes,
                                scope: scope
                            })
                        })
                    }
                }
            }
            console.log(data)
            resolve(data)
        })
    })
}
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