The Qt 6 Book

# JS Objects

While working with JS there are some objects and methods which are more frequently used. This is a small collection of them.

  • Math.floor(v), Math.ceil(v), Math.round(v) - largest, smallest, rounded integer from float

  • Math.random() - create a random number between 0 and 1

  • Object.keys(o) - get keys from object (including QObject)

  • JSON.parse(s), JSON.stringify(o) - conversion between JS object and JSON string

  • Number.toFixed(p) - fixed precision float

  • Date - Date manipulation

You can find them also at: JavaScript reference (opens new window)

Here some small and limited examples of how to use JS with QML. They should give you an idea how you can use JS inside QML

Item {
    id: root
    Component.onCompleted: {
        var keys = Object.keys(root);
        for(var i=0; i<keys.length; i++) {
            var key = keys[i];
            // prints all properties, signals, functions from object
            console.log(key + ' : ' + root[key]);
        }
    }
}

# Parse an object to a JSON string and back

Item {
    property var obj: {
        key: 'value'
    }

    Component.onCompleted: {
        var data = JSON.stringify(obj);
        console.log(data);
        var obj = JSON.parse(data);
        console.log(obj.key); // > 'value'
    }
}

# Current Date

Item {
    Timer {
        id: timeUpdater
        interval: 100
        running: true
        repeat: true
        onTriggered: {
            var d = new Date();
            console.log(d.getSeconds());
        }
    }
}

# Call a function by name

Item {
    id: root

    function doIt() {
        console.log("doIt()")
    }

    Component.onCompleted: {
        // Call using function execution
        root["doIt"]();
        var fn = root["doIt"];
        // Call using JS call method (could pass in a custom this object and arguments)
        fn.call()
    }
}

← Creating a JS Console →