I'm trying to figure this out but can't seem to on my own...
I'm playing with Web SQL DBs and I can't get a loop to work properly with it.
I use:
for (var i=0; i<=numberofArticles-1; i++){
db.transaction(function (tx) {
tx.executeSql('INSERT INTO LOGS (articleID) VALUES (?)', [i]);
});
};
And I get only 5's.. I don't get the incremental i values.
Can anyone suggestion what I'm doing wrong and what I should be thinking about?
Do it the other way around:
<script>
numberofArticles = 5;
db = openDatabase("websql", "0.1", "web-sql testing", 10000);
db.transaction(function(tx) {
tx.executeSql('CREATE TABLE IF NOT EXISTS LOGS (id unique, articleID int)');
});
db.transaction(function (tx) {
for (var i=0; i<=numberofArticles-1; i++){
tx.executeSql('INSERT INTO LOGS (articleID) VALUES (?)', [i]);
};
});
</script>
And the alternative, the proper way with the loop outside which is unnecessary in this case
for (var i=0; i<=numberofArticles-1; i++){
(function(i) {
db.transaction(function (tx) {
tx.executeSql('INSERT INTO LOGS (articleID) VALUES (?)', [i]);
});
})(i);
};
It looks like the function is asynchronous, and that by the time tx.executeSql fires, the loop have finished looping and i has been changed several times.
You can solve this with a closure.
for (var i=0; i<=numberofArticles-1; i++){
function (value) {
db.transaction(function (tx) {
tx.executeSql('INSERT INTO LOGS (articleID) VALUES (?)', [value]);
});
}(i); // <-- CALL the function
};
(any args) on the end of it. function (){}() is just like function foo() {}; foo(); except it doesn't keep foo around for later use.