Data Storage - Introducing HTML5 - page 189

// div 1000 to get to seconds
});
});
}
The INSERT statement is the most important part, and now you
can see how the field arguments work:
tx.executeSql('INSERT INTO tweets (id, screen_name, date,
¬ text) VALUES (?, ?, ?, ?)', [tweet.id, tweet.from_user,
¬ time / 1000, tweet.text]);
Each “?” in the INSERT statement maps to an item in the array
that is passed in as the second parameter to executeSql . So
the first “?” maps to tweet.id , the second to tweet.from_user ,
and so on.
Yo u c a n a l is o is e e t h a t I ' v e d i v i d e d t h e t i m e b y 1 , 0 0 0 ; t h i is i is
because JavaScript time is counted in milliseconds, whereas
SQLite wants it to be in whole seconds. This is only important
for your query later on in the code where you show tweets that
are 5 minutes old. This matters because you're storing dates
as integers, and one second using JavaScript's getTime method
gives us 1,000, whereas one second using SQLite gives us 1. So
you divide by 1,000 to store seconds rather than milliseconds.
Finally, when the radio buttons are clicked, you call the show
function with the amount of time as the argument:
var tweetEl = document.getElementById('tweets');
function show(amount) {
db.transaction(function (tx) {
tx.executeSql('SELECT * FROM tweets' + (amount !=
¬ 'all' ? ' WHERE date > strftime(“%s”, “now”, “-' +
¬ amount + ' minutes”)' : ''), [], function
¬ (tx, results) {
var html = [],
len = results.rows.length;
for (var i = 0; i < len; i++) {
html.push('<li>' + results.rows.item(i).text +
¬ '</li>');
}
tweetEl.innerHTML = html.join('');
});
});
}