I'm trying to get my WebSQL database to popluate using a JSON array (Object is called myJSONObject, array is called costcodes).
The function runs on click, the database successfully creates, but the data is not inserted into the database. It doesn't even throw and error, it just doesn't do anything.
My initial thought was that the data isn't escaped properly, but I don't know exactly where/how to escape it. So I'm stumped.
localDB = null;
function initDB()
{
if (localDB==null)
{
var shortName = 'Costcode';
var version = '1.0';
var displayName = 'Costcode';
var maxSize = 217802; // in bytes
localDB = window.openDatabase(shortName, version, displayName, maxSize);
}
}
function buildTable()
{
var sQuery = 'CREATE TABLE IF NOT EXISTS Costcode ('+
'id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,' +
'cost_code_no VARCHAR NULL,' +
'row_unique_no VARCHAR NULL,' +
'cost_class_no VARCHAR NULL,' +
'Table_Version VARCHAR DEFAULT "1.0");';
try
{
initDB();
localDB.transaction(function(transaction)
{
transaction.executeSql(sQuery, []);
console.log('sucess');
});
}
catch (e)
{
alert("Error: Unable to create table 'x" + "' " + e + ".");
return;
}
}
function exeSQLFast()
{
initDB();
localDB.transaction(function(transaction)
{
for (var x = 0; x <myJSONObject.costcodes.length; x++)
{
var costcodeno = myJSONObject.costcodes[x].cost_code_no;
var rowuniqueid = myJSONObject.costcodes[x].row_unique_id;
var costclassno = myJSONObject.costcodes[x].cost_class_no;
console.log(costcodeno);
console.log(rowuniqueid);
console.log(costclassno);
transaction.executeSql('INSERT INTO Costcode (cost_code_no, row_unique_id, cost_class_no) VALUES (? , ? , ?)',
[costcodeno,
rowuniqueid,
costclassno]
, function(transaction, results)
{
console.log(costcodeno);
console.log('hooray');
}
)};
}
)}
</script>
</head>
<body onLoad="buildTable();">
<input type="button" onClick="exeSQLFast();" value='button'>
</body>
</html>
The console log shows that the variables are all being properly defined, but it's not running the insert statement. Any ideas?
Here's an example of myJSONObject.costcodes[2]
cost_class_no: " 3"
cost_code_no: " 1000"
row_unique_id: 335
That looks like a problem doesn't it...
The problem was that I called the row_unique_no column row_unique_id in the insert statement. Now I feel stupid.
But if anyone is curious how to populate a WebSQL database properly, this is how you do it. Just don't mistype the column names.
Related
I have a TableA containing brands with names, names are for example: brand1, 123, brand2, 999.
I want to select names, create button with id=name and pass the name to function brandOnOff(name), then alert the name I passed.
When I press button "123" or "999" it works correctly. But buttons "brand1" and "brand2" don't work - they alert: [object HTMLButtonElement]. I think I have I problem with "" and '' and I don't know how to fix it...
When I alert(document.getElementById("demo").innerHTML) I get:
<button id="brand1" onclick="brandOnOff(brand1)">brand1</button><button id="123" onclick="brandOnOff(123)">123</button><button id="brand2" onclick="brandOnOff(brand2)">brand2</button><button id="999" onclick="brandOnOff(999)">999</button>
and I think it should be like: ... onclick="brandOnOff("brand1")"... etc --- Quotation-mark then name then Quotation-mark
but when I try to add Quotation-marks there's an error "Unexpected end of input" and I keep messing it up.
Can somebody help me please? I'm stuck :(
Here is the code:
DB.transaction(function (tx) {
tx.executeSql('SELECT * FROM TableA', [], function (tx, rs) {
var brand;
for (i = 0; i < brands; i++)
{
brand = rs.rows.item(i).name;
document.getElementById("demo").innerHTML = document.getElementById("demo").innerHTML + '<button id="' + brand + '" onclick="brandOnOff(' + brand + ')">' + brand + '</button>';
}
}, function (tx, error) {
console.log('SELECT error: ' + error.message);
});
});
function brandOnOff(brandName) {
alert(brandName);
}
Your main issue is caused by trying to use inline event handlers, when these are generally considered obsolete and addEventHandler is universally supported.
You should also split out your logic somewhat into smaller testable units, that separate HTML page generation from database code:
// event handler - passed the clicked element in ev.target
function brandOnOff(ev) {
alert(ev.target.id);
}
// takes an array of brand names and generates a button for each
function buildBrandButtons(brands) {
let demo = document.getElementById('demo');
brands.forEach(brand => {
let button = document.createElement('button');
button.id = brand;
button.textContent = brand;
button.addEventListener('click', brandOnOff);
demo.addChild(button);
});
}
// converts a result set into an array of the specified field's values
function getResultSetField(rs, field) {
let values = [];
for (let i = 0; i < rs.rows.length; ++i) {
values.push(rs.rows.item(i)[field]);
}
return values;
}
// the meat - gets the brand names, builds the buttons
function processBrands(tx, rs) {
let brands = getResultSetField(rs, 'name');
buildBrandButtons(brands);
}
// generic error handler
function selectError(tx, error) {
console.log('SELECT error: ' + error.message);
}
// the actual database work
DB.transaction(tx => {
tx.executeSql('SELECT * FROM TableA', [], processBrands, selectError);
});
This may look like a lot more code, but each part has a specific responsibility, and some of these functions may be re-used later (e.g. selectError, getResultSetField).
NB: no nested quote marks, or indeed any that aren't around a string constant.
I am using MongoDB and Node.JS, I am trying to get data out of my MongoDB and show into my html page which I have working with the below code however this just brings back ALL entries in no particular order:
server.js
// This is for getting the list of all players from my DB
app.get("/getPlayers", function(request, response) {
db.getPlayers().then(function(players){
console.log(players);
response.send(players);
});
});
leadership.html
<script>
$(function() {
$.get("http://localhost:9000/getPlayers", {}, function (res) {
let data = res;
console.log(res);
for (i = 0; i < data.length; i++) {
let name = data[i].name;
let score = data[i].score;
console.log(data[i].name);
$("#leadership").append("<tr><td class=\"name\">"
+ data[i].name + "</td><td class=\"score\">"
+ data[i].score + "</td></tr>");
}
});
});
</script>
After looking at W3 Schools I tried to alter the code to this:
db.getPlayers().sort().limit(10).then(function(players)
However my Chrome console brings back an internal server error 500. Can someone point out how I can sort by LARGEST NUMBER first, then LIMIT the results to say 10? Within the database there is a collection called players, which holds name and score
db.js
var Player = mongoose.model("Player", {name: String, score: Number});
module.exports.Player = Player;
Try something like this.
Order, sort and limit can be passed from front end or change default values after : mark.
Players is imported model, you can do it this way or use method in the model itself.
app.post('/api/players',(req,res)=>{
let order = req.body.order ? req.body.order : "-1";
let sortBy = req.body.sortBy ? req.body.sortBy : "_id";
let limit = req.body.limit ? parseInt(req.body.limit) : 100;
Players.
find().
sort([[sortBy,order]]).
limit(limit).
exec((err,players)=>{
if(err) return res.status(400).send(err);
res.status(200).json({
size: players.length,
players
})
})
})
I am trying to decompose a user's get request and put it in a variable named query. then pass the var query into the sequelize's findAll method using it's where clause, it seems like Sequelize thinks i am looking for a table CALLED query when in reality i am trying to pass the object. I'm sorry if i can not explain very well, but here is the code and the error:
var info = [];
//link example: localhost:8081/filter/?descripiton=san+francisco&houseType=house&numOfBedroom=3&numOfBathroom=2&houseSize=500&price=1200
exports.filterListings = function(req) {
//create an object literal which we will return, and has a nested object named filteredList inside.
//filteredList contains an array named listings where we will put listings that match our filter inside
let response = {
filteredList: {listings: []},
};
//now we need to see how the user wants us to filter the listings
const query = req.query;
//do some logic where we decompose query
if(query.descripiton != undefined) {
//info = info + 'descripiton: ' + query.descripiton+', ';
info.push('descripiton: ' + query.descripiton+', ');
console.log(info);
}
if(query.houseType != undefined) {
//info = info + 'houseType: ' + query.houseType+', ';
info.push('houseType: ' + query.houseType+', ');
//console.log(info);
}
if(query.numOfBedroom != undefined) {
//info = info + 'numOfBedroom: ' + query.numOfBedroom+', ';
info.push('numOfBedroom: ' + query.numOfBedroom+', ');
}
if(query.numOfBathroom != undefined) {
//info = info + 'numOfBathroom: ' + query.numOfBathroom+', ';
info.push('numOfBathroom: ' + query.numOfBathroom+', ');
}
if(query.houseSize != undefined) {
//info = info + 'houseSize: ' + query.houseSize+', ';
info.push('houseSize: ' + query.houseSize+', ');
}
if(query.price != undefined) {
//info = info + 'price: ' + query.price;
info.push('price: ' + query.price);
}
and then when i try to pass the info variable
listingModel.findAll({
//error because it wont recognize the variable search nor will it recognize info
where: {info}
}).then(listings => {
// so we loop through listings and insert what we have found into the response (which we are going to return)
for(var i = 0; i < listings.length; i++) {
response.filteredList.listings.push(listings[i]);
}; // loop where we insert data into response done
I want it to find all listings based on the dynamic query but i am getting the error:
Unhandled rejection SequelizeDatabaseError: Unknown column 'Listing.info' in 'where clause'
Thank you very much for the potential help!
Let's try to sort through your problems one by one. Sorry for the pun :p
Instead of using multiple if for creating your filtered list. Use for ... in. Then use that array of objects along with Sequelize.Op to create your query.
Example:
const Op = require('sequelize').Op;
const whereClause = [];
const query = req.query;
for(const key in query) {
if(query[key] !== '' && query[key] !== null) {
//object will be pushed to the array like "houseType:big"
whereClause.push({key:query[key]})
}
}
//you now have the where clause
//use it in your query with Op.and
listingModel.findAll({
where: {
[Op.and]: whereClause,
}
});
More info about querying with Sequelize - Operators
I wrote a ~50 lines script to perform housekeeping on MySQL databases. I'm afraid my code exhibits anti-patterns as it rapidly escalates to an unreadable mess for the simple functions it performs.
I'd like some opinions for improving readability.
The full script is at the bottom of this post to give an idea.
Spotlight on the problem
The excessive nesting is caused by patterns like this repeated over and over: (snippet taken from script)
sql.query("show databases")
.then(function(rows) {
for (var r of rows) {
var db = r.Database;
(function(db) {
sql.query("show tables in " + db)
.then(function(rows) {
// [...]
}
})(db);
}
});
I'm nesting one promise under the other within both a for loop and a closure. The loop is needed to iterate across all results from sql.query(), and the closure is necessary to pass the value of db to the lower promise; without the closure, the loop would complete even before the nested promise executes at all, so db would always contain only the last element of the loop, preventing the nested promise from reading each value of db.
Full script
var mysql = require("promise-mysql");
var validator = require("mysql-validator"); // simple library to validate against mysql data types
var ignoreDbs = [ "information_schema" ],
multiplier = 2, // numeric records multiplier to check out-of-range proximity
exitStatus = {'ok': 0, 'nearOutOfRange': 1, 'systemError': 2};
(function() {
var sql,
mysqlHost = "localhost",
mysqlUser = "user",
mysqlPass = "";
mysql.createConnection({
host: mysqlHost,
user: mysqlUser,
password: mysqlPass
}).then(function(connection) {
sql = connection;
})
.then(function() {
sql.query("show databases")
.then(function(rows) {
for (var r of rows) {
var db = r.Database;
if (ignoreDbs.indexOf(db) != -1) continue;
(function(db) {
sql.query("show tables in " + db)
.then(function(rows) {
for (var r of rows) {
var table = r["Tables_in_" + db];
(function(table) {
sql.query("describe " + db + "." + table)
.then(function(rows) {
for (var r of rows) {
(function(r) {
var field = r.Field,
type = r.Type, // eg: decimal(10,2)
query = "select " + field + " from " + db + "." + table + " ";
if (table != "nonce") query += "order by date desc limit 1000";
sql.query(query)
.then(function(rows) {
for (var r of rows) {
var record, err;
// remove decimal part, only integer range is checked
record = Math.trunc(r[field]);
err = validator.check(record * multiplier, type);
if (err) {
console.log(err.message);
process.exit(exitStatus.nearOutOfRange);
}
}
});
})(r);
}
});
})(table);
}
});
})(db);
}
});
})
.then(function() {
// if (sql != null) sql.end(); // may not exit process here: sql connection terminates before async functions above
//process.exit(exitStatus.ok); //
});
})();
Trivia
The purpose of the script is to automatically and periodically monitor if any record stored in any row, table and database in MySQL is approaching the out-of-range limit for its specific data type. Several other processes connected to MySQL continuously insert new numeric data with increasing values and nonces; this script is a central point where to check for such numeric limits. The script would then be attached to Munin for continuous monitoring and alerting.
Update: Revised script
As suggested by #Kqcef I modularized the anonymous functions out of the promise nest, and used let to avoid the explicit nesting of an additional function to preserve variable context.
Still this is excessively verbose, previously I wrote the same script in Bash in about 40 lines, but performance was screaming for a port to nodejs.
"use strict";
var mysql = require("promise-mysql");
var validator = require("mysql-validator"); // a simple library to validate against mysql data types
var ignoreDbs = [ "information_schema" ],
multiplier = 2, // numeric records multiplier to check out-of-range proximity
exitStatus = {'ok': 0, 'nearOutOfRange': 1, 'systemError': 2};
var mysqlHost = "localhost",
mysqlUser = "btc",
mysqlPass = "";
// return array of DBs strings
function getDatabases(sql) {
return sql.query("show databases")
.then(function(rows) {
var dbs = [];
for (var r of rows)
dbs.push(r.Database);
return dbs;
});
}
// return array of tables strings
function getTables(sql, db) {
return sql.query("show tables in " + db)
.then(function(rows) {
var tables = [];
for (var r of rows)
tables.push(r["Tables_in_" + db]);
return tables;
});
}
// return array of descriptions
function getTableDescription(sql, db, table) {
return sql.query("describe " + db + "." + table)
.then(function(rows) {
var descrs = [];
for (var r of rows) {
descrs.push({ 'field': r.Field, // eg: price
'type': r.Type}); // eg: decimal(10,2)
}
return descrs;
});
}
// return err object
function validateRecord(record, type) {
var record, err;
if (typeof record != "number") {
console.log("error: record is not numeric.");
process.exit(exitStatus.systemError);
}
// remove decimal part, only integer range is checked
record = Math.trunc(record);
err = validator.check(record * multiplier, type);
return err;
}
(function() {
var sql;
mysql.createConnection({
host: mysqlHost,
user: mysqlUser,
password: mysqlPass
}).then(function(connection) {
sql = connection;
})
.then(function() {
return getDatabases(sql)
})
.then(function(dbs) {
dbs.forEach(function(db) {
if (ignoreDbs.indexOf(db) != -1) return;
getTables(sql, db)
.then(function(tables) {
tables.forEach(function(table) {
getTableDescription(sql, db, table)
.then(function(descrs) {
descrs.forEach(function(descr) {
let field = descr.field,
type = descr.type,
query = "select " + descr.field + " from " + db + "." + table + " ";
if (table != "nonce") query += "order by date desc limit 1000";
sql.query(query)
.then(function(rows) {
rows.forEach(function(row) {
let err = validateRecord(row[field], type);
if (err) {
console.log(err.message);
process.exit(exitStatus.nearOutOfRange);
}
});
});
});
});
});
});
});
});
/*
.then(function() {
//if (sql != null) sql.end();
//process.exit(exitStatus.ok);
});
*/
})();
I agree with Jaromanda in terms of using let in your for loops to block scope the values and avoid your usage of an immediately-invoked function, which, while totally fine in terms of functionality, is decidedly less readable.
In terms of best practices and avoiding anti-patterns, one of the most important things you can strive for in terms of writing 'good' code is building modularized, reusable blocks of code. As it stands, your code has 5 or 6 anonymous functions that exist nowhere but within your chain of promise callbacks. If you were to declare those as functions outside of that chain, not only does that improve the maintainability of your code (you can test each individual one), but, if their names are clearly indicative of their purposes, would make for a very readable promise chain.
(Updated based on User Question)
Rather than leaving inner functions...
function getTableDescription(sql, db, table) {
return sql.query("describe " + db + "." + table)
.then(function(rows) {
var descrs = [];
for (var r of rows) {
descrs.push({ 'field': r.Field, // eg: price
'type': r.Type}); // eg: decimal(10,2)
}
return descrs;
});
}
...you can easily strip that out so that your code is self-documenting:
function collectDescriptionsFromRows(rows) {
var descriptions = [];
for (var row of rows) {
descriptions.push({'field': row.Field, 'type': row.Type});
}
return descriptions;
}
function getTableDescription(sql, db, table) {
return sql.query("describe " + db + "." + table)
.then(collectDescriptionsFromRows);
}
Also, if you ever find yourself doing data collection from one array to another, it's extremely helpful to get used to using built-in higher order functions (map, filter, reduce). Instead of the collectDescriptionsFromRows I just listed, it could be simplified to:
function collectDescriptionsFromRows(rows) {
return rows.map(row => { 'field': row.Field, 'type': row.Type});
}
Much less verbose, much more readable. Your code and promise-chain will shrink and read more like a step-by-step list of instructions if you continue to extract those anonymous functions in the chain. Anywhere you see function(...there is more extracting to do! You can also do some damage (positively) by extracting all the data you need to begin with and use local logic to boil it down to what you need, rather than making several queries. Hope this helps.
I tried to insert some data into web sql database.But I met a problem.
My code :
database();
for(var i=0;i<m.length;i++){
showid = m[i].id;
showtitle = m[i].title;
insert();
}
function database(){
//open the database
db = window.openDatabase("youyanchu", "1.0","youyanchu",500000);
db.transaction(function(tx) {
var table = tx.executeSql("CREATE TABLE showList (id int PRIMARY KEY, title NVARCHAR, finishDate NVARCHAR, status NVARCHAR, tkCount NVARCHAR )");
});
}
//INTEGER NOT NULL PRIMARY KEY
function insert(){
db.transaction(function(ar) {
ar.executeSql("INSERT INTO showList (id, title,finishDate,status) values(?,?,?,?)", [showid,showtitle,'aaa','bbb']);
});
}
m.length is 3 and "m" should be
aaa = {'id':'999','title':'ninini'}
bbb = {'id':'888','title':'ninini'}
ccc = {'id':'777','title':'ninini'}
At last,just "ccc" display in the web sql.
How to insert all data into the database?What mistake I made in the code?
Since tx.executeSql is asynchronous, I believe your loop finishes before the first insert runs.
Hence showid and showtitle will always have the last values of the object m
Try this instead:
for(var i=0;i<m.length;i++){
insert(m[i].id, m[i].title);
}
function insert(id, title){
db.transaction(function(tx) {
txexecuteSql("INSERT INTO showList (id, title,finishDate,status) values(?,?,?,?)", [id, title,'aaa','bbb']);
});
}