make player jump when tap on screen

 using UnityEngine;
 using System.Collections;
 
 public class Playercontroller : MonoBehaviour {
 
     public float movespeed = 4f;
     public float jumpspeed = 7f;
 
     private Rigidbody2D myrigidbody;
 
     // Use this for initialization
     void Start () {
         myrigidbody = GetComponent<Rigidbody2D> ();
 
     }
     
     // Update is called once per frame
     void Update () 
     {
         myrigidbody.velocity = new Vector2 (movespeed, myrigidbody.velocity.y);
 
         if (Input.GetKeyDown (KeyCode.Space) ) 
         {
             myrigidbody.velocity = new Vector2 (myrigidbody.velocity.x, jumpspeed);
         }
     }
 }

I am using this script to make my player jump using space button . i need mobile touch to make my player jump i don't know how to do this.....so help me.