How to access the properties of a Repeater's children in QML

I have to change imgx.x value, should I use JavaScript? Or is there another way?

Row {
    Repeater {
        id:mmm
        model : 10
        Rectangle{
            clip: true
            width: 54
            height: 80
            color:"transparent"
            Image {
                id:imgx
                //x:-160
                //x:-105
                //x:-50
                x:0
                source: "images/tarama_lights.png"
            }
        }
    }
}

You have to add a property to the direct child of the Repeater (Rectangle in your case) and set it as a target for the property in the internal child (Image in your case). You can then use mmm.itemAt(<index of the element>).<property> = value.

Repeater {
    id:mmm
    model : 10
    Rectangle{
        clip: true
        width: 54
        height: 80
        color:"transparent"
        property int imageX: 0 //adding property here

        Image {
            id:imgx
            x: parent.imageX //setting property as the target
            source: "images/tarama_lights.png"
        }
    }
}

You can then change the property like this:

onPropertyChange: {
    mmm.itemAt(index).imageX = newValue //the index defines which rectangle you change
}