Change Font Size

var config = {
    type: Phaser.AUTO,
    parent: 'phaser-example',
    width: 800,
    height: 600,
    scene: {
        preload: preload,
        create: create
    }
};

var game = new Phaser.Game(config);

function preload() 
{
    this.load.bitmapFont('atari', 'assets/fonts/bitmap/gem.png', 'assets/fonts/bitmap/gem.xml');
}

function create() 
{
    var text = this.add.bitmapText(400, 300, 'atari', '', 16).setOrigin(0.5).setCenterAlign().setInteractive();

    text.setText([
        'Phaser 3',
        'BitmapText',
        'Click to change size'
    ]);

    this.input.on('pointerup', function () {

        text.setFontSize(text.fontSize + 2);
        text.setOrigin(0.5);

    });
}