Question

So I read the tutorial from some web, and they did something like this.

function populateDB(tx) {
     tx.executeSql('DROP TABLE IF EXISTS DEMO');
     tx.executeSql('CREATE TABLE IF NOT EXISTS DEMO (id unique, data)');
     tx.executeSql('INSERT INTO DEMO (id, data) VALUES (1, "First row")');
     tx.executeSql('INSERT INTO DEMO (id, data) VALUES (2, "Second row")');
}

function errorCB(err) {
    alert("Error processing SQL: "+err.code);
}

function successCB() {
    alert("success!");
}

var db = window.openDatabase("Database", "1.0", "Cordova Demo", 200000);
db.transaction(populateDB, errorCB, successCB);

In the last line, they called the method transaction from object db, and there are 3 functions in the argument field, but isn’t the functions populateDB, errorCB both need an argument as well? Where is that argument being called?

Answer 1

The database runtime will call those functions when it wants to, and it will pass in the parameters. In the “db.transaction” function call, you’re passing in references to the functions. At that point, function parameters are not needed because you’re just identifying which functions to call.