IndexedDB 封装

class DB{
    /** 构造函数 */
    constructor(dbName){
        this.dbName = dbName;
    }
    
    /**
     * 选择表单
     */
    table(tableName, keys, version){
        version = version || 1;
        this.tableName = tableName;
        this.request = indexedDB.open(this.dbName, version);
        return new Promise((resolve, reject) => {
            this.request.onsuccess = (event) => {
                this.db = event.target.result;
                
                resolve(this);
            }
            
            this.request.onupgradeneeded = (event) => {
                this.db = event.target.result;
                var objectStore;
                
                // 排列组合组装索引
                var groups = [];
                for(let i=0; i< keys.length; i++){
                    var arr = []; 
                    arr.push([keys[i]]);
                    for(let j=0; j< groups.length; j++){
                        arr.push([...groups[j], keys[i]]);
                    }
                    groups = groups.concat(arr);
                }
                if(!this.db.objectStoreNames.contains(tableName)){
                    objectStore = this.db.createObjectStore(tableName, {keyPath: 'id'});
                    groups.forEach(item => {
                        var idx = item.join('_');
                        objectStore.createIndex(idx, item, {unique: false});
                    });
                    
                }
                else{
                    objectStore = this.request.transaction.objectStore(tableName);
                    
                    var newIndexNames = [];
                    groups.forEach(item => {
                        var idx = item.join('_');
                        newIndexNames.push(idx);
                        if(!objectStore.indexNames.contains(idx)){
                            objectStore.createIndex(idx, item, {unique: false});
                        }
                    });
                    var delIndexNames = [];
                    for(var i=0; i<objectStore.indexNames.length; i++){
                        var item = objectStore.indexNames.item(i);
                        if(!newIndexNames.includes(item)){
                            delIndexNames.push(item);
                        }    
                    }
                    
                    // 删除索引
                    delIndexNames.forEach(item => {
                        console.log('del:' + item);
                        objectStore.deleteIndex(item);
                    });
        
                }
                
            }
            
            this.request.onerror = (event) => {
                reject(event);
            }
        });
    }
    

    
    /**
     * 新增数据
     */
    add(item){
        return new Promise((resolve, reject) => {
            var request = this.db.transaction([this.tableName], 'readwrite')
            .objectStore(this.tableName)
            .add(item);
            
            request.onsuccess = (event) => {
                resolve(event);
            }
            request.onerror = (event) => {
                reject(event);
            }
            
        });
    }
    
    /**
     * 通过ID获取
     */
    get(id){
        return new Promise((resolve, reject) => {
            var transaction = this.db.transaction([this.tableName]);
            var objectStore = transaction.objectStore(this.tableName);
            var request = objectStore.get(id);
            request.onsuccess = (event) => {
                resolve(event.target.result);
            }
            request.onerror = (event) => {
                reject(event);
            }
        });
    }
    
    /** 获取所有 */
    findAll(){
        return new Promise((resolve, reject) => {
            var transaction = this.db.transaction([this.tableName]);
            var objectStore = transaction.objectStore(this.tableName);
            
            var items = [];
            objectStore.openCursor().onsuccess = async (event) => {
                var cursor = event.target.result;
                if(cursor){
                    console.log(cursor);
                    items.push(cursor.value);
                    cursor.continue();
                }
                else{
                    resolve(items);
                }
                
            }
            
        });
    }
    
    /**
     * 查询列表
     */
    findList(filter){
        return new Promise((resolve, reject) => {
            var keys = Object.keys(filter);
            var values = Object.values(filter);
            
            
            var transaction = this.db.transaction([this.tableName]);
            var objectStore = transaction.objectStore(this.tableName);
            var index = objectStore.index(keys.join('_'));
            
            var items = [];
            
            index.openCursor(IDBKeyRange.only(values)).onsuccess = async (event) => {
                var cursor = event.target.result;
                if(cursor){
                    items.push(cursor.value);
                    cursor.continue();
                }
                else{
                    resolve(items);
                }
                
            }
            
        });
    }
}
var db = new DB('TTD');
db.table('person', ['name', 'age'], 11)
.then(() => {
    //return db.add({id: 6, name: '王五', age: 25, email: 'zhangsan@email.com'})
})
.then(()=>{
    return db.get(11);
}).then(res => {
    console.log(res);
}).then(() => {
    return db.findAll();
}).then(res =>{
    console.log(res);
}).then(() =>{
    return db.findList({age: 25})
}).then(res =>{
    console.log(res);
});