var target: Transform;
    private var agent: NavMeshAgent;
    function Start () {
        agent = GetComponent.<NavMeshAgent>();
        var path: NavMeshPath;
        agent.CalculatePath(target.position, path);
        
        if (path.status == NavMeshPathStatus.PathPartial) {
            // The target cannot be reached...
        }
    }

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public Transform target;
    private NavMeshAgent agent;
    void Start() {
        agent = GetComponent<NavMeshAgent>();
        NavMeshPath path;
        agent.CalculatePath(target.position, path);
        if (path.status == NavMeshPathStatus.PathPartial) {
        }
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public target as Transform

    private agent as NavMeshAgent

    def Start():
        agent = GetComponent[of NavMeshAgent]()
        path as NavMeshPath
        agent.CalculatePath(target.position, path)
        if path.status == NavMeshPathStatus.PathPartial:
            pass