I want to make it so that I can't jump in midair.

Phaser 3
1 
  const config = {
      type: Phaser.AUTO,
      backgroundColor: "#48C4F8",
      width: 960,
      height: 540,
      pixelArt: true,
      scale: {
        parent: 'game',
        autoCenter: Phaser.Scale.CENTER_BOTH
      },
      physics: {
        default: 'matter',
        matter: {
          gravity: { y: 2 },
          debug: false
        }
      },
      scene: {
        preload: preload,
        create: create,
        update: update
      }
    };

 
    var player;
    var stars;
    var bombs;
    var platforms;
    var cursors;
    var score = 0;
    var gameOver = false;
    var scoreText;

    var game = new Phaser.Game(config);
    function preload() {
      this.load.image('ground', 'assets/platform.png');
      this.load.image('star', 'assets/star.png');
      this.load.image('bomb', 'assets/bomb.png');
      this.load.spritesheet('dude',
        'assets/dude.png',
        { frameWidth: 32, frameHeight: 48 }
      );
      this.load.image('spike', 'assets/images/spike.png');
      this.load.atlas('player', 'assets/images/kenney_player.png', 'assets/images/kenney_player_atlas.json');
      this.load.image('tiles', 'assets/tilesets/platformPack_tilesheet.png');
      this.load.tilemapTiledJSON('map', 'assets/tilemaps/level1.json');
    }

    function create() {
      player = this.matter.add.sprite(40, 0, "player", 4);
      this.anims.create({
        key: 'walk',
        frames: this.anims.generateFrameNames('player', {
          prefix: 'robo_player_',
          start: 2,
          end: 3,
        }),
        frameRate: 10,
        repeat: -1
      });
      this.anims.create({
        key: 'idle',
        frames: [{
          key: 'player',
          frame: 'robo_player_0'
        }],
        frameRate: 10,
      });
      this.anims.create({
        key: 'jump',
        frames: [{
          key: 'player',
          frame: 'robo_player_1'
        }],
        frameRate: 10,
      });
      this.cursors = this.input.keyboard.createCursorKeys();
      const map = this.make.tilemap({
        key: 'map'
      });
      const tileset = map.addTilesetImage('kenny_simple_platformer', 'tiles');
      const platforms = map.createStaticLayer('Platforms', tileset, 0, 0);
      platforms.setCollisionByProperty({ collides: true });
      this.matter.world.convertTilemapLayer(platforms);
      platforms.setCollisionByExclusion(-1, true);
      platforms.setCollisionByProperty({ collides: true });
      this.matter.world.convertTilemapLayer(platforms);
      this.matter.add.gameObject(player);
      this.matter.world.on("collisionactive", (player, platforms) => {
        skaterTouchingGround = true;
      });
    }

    function update() {
      if (this.cursors.left.isDown) {
        player.setVelocityX(-3);
        player.play('walk', true);
      } else if (this.cursors.right.isDown) {
        player.setVelocityX(3);
        player.play('walk', true);
      }

    
      if ((this.cursors.space.isDown || this.cursors.up.isDown) && skaterTouchingGround) {
        player.setVelocityY(-3);
        player.play('jump', true);
      }```