how to add function to ui button through code unity code example

Example 1: unity assign button onclick

public Button yourButton;	

void Start () 
{
	Button btn = yourButton.GetComponent<Button>(); //Grabs the button component
	btn.onClick.AddListener(TaskOnClick); //Adds a listner on the button
}	
void TaskOnClick()
{
	Debug.Log ("You have clicked the button!");
}

Example 2: how to code button click unity

using UnityEngine;
using UnityEngine.UI;
using System.Collections;
public class ClickExample : MonoBehaviour {
	public Button yourButton;	
    
    void Start () {
		Button btn = yourButton.GetComponent<Button>();
		btn.onClick.AddListener(TaskOnClick);
	}	
    void TaskOnClick(){
		Debug.Log ("You have clicked the button!");
	}
}