我使用以下代码从Web sql数据库中获取分层数据：
...
function getResult(query,data,callback){
db.transaction(function(tx) {
tx.executesql(query,function(tx,result) {
callback(result);
});
});
}
function findChildren(id){
getResult("SELECT * FROM my_table WHERE parent_id=?",[id],function(result){
for (var i = 0,item = null; i < result.rows.length; i++) {
item = result.rows.item(i);
data.push(item);
findChildren(item.id);
}
});
}
var data = Array();
getResult("SELECT * FROM my_table WHERE name like ?",["A"],function(result){
for (var i = 0,item = null; i < result.rows.length; i++) {
item = result.rows.item(i);
data.push(item);
findChildren(item.id);
}
});
...
如何检测执行是否已完成？
解决方法
使用findChildren的回调和打开事务的计数器：
function findChildren(id,callback){
getResult("SELECT * FROM my_table WHERE parent_id=?",function(result){
var results = [],results.finished = 0;
len = result.rows.length;
for (var i = 0; i < len; i++) (function(i) {
var item = result.rows.item(i);
...
...
findChildren(item.id,function(result) {
results[i] = result;
if (++results.finished == len)
callback(results);
});
})(i);
});
}
getResult("SELECT * FROM my_table WHERE name like ?",function(result){
var results = [],results.finished = 0,len = result.rows.length;
for (var i = 0; i < len; i++) (function(i) {
var item = result.rows.item(i);
...
...
findChildren(item.id,function(result) {
results[i] = result;
if (++results.finished == len) {
// now results contains a nice tree of arrays with children ids
// do something with it
}
});
})(i);
});
