Type or namespace 'CharacterMotor' cannot be found

This is my RunningSound code, which uses triggers to play ‘walking’ and ‘running’ sounds. The problem is, I have no idea how to fix the CharacterMotor error I keep getting at runtime. The CharacterMotor and this file are in the same folder in the Standard Assets file, and the file below is a C# file, while the CharacterMotor is a Javascript file. Any suggestions on what I should do? Thank you in advance for your help.

using UnityEngine;
using System.Collections;
using CharacterMotor;//Unsure of this area, does not seem to do anything. 
//Still here to show it does not work.

[RequireComponent(typeof(AudioSource))]

public class WalkingSoundScript : MonoBehaviour {
 
AudioClip walk;
AudioClip run;
 
float walkAudioSpeed = 0.4f;
float runAudioSpeed = 0.2f;
 
private float walkAudioTimer = 0.0f;
private float runAudioTimer = 0.0f;
 
bool  isWalking = false;
bool  isRunning = false;
 
float walkSpeed = 7; // regular speed
float runSpeed = 20; // run speed
 
private CharacterController chCtrl;
private CharacterMotor chMotor;//Note that CharacterMotor is a Javascript file, and is not considered an object.
 
void  Start (){
    chCtrl = GetComponent<CharacterController>();
    chMotor = GetComponent<CharacterMotor>();
}
 
void  Update (){
    SetSpeed();
 
    if ( chCtrl.isGrounded )
    {
        PlayFootsteps();
    }
    else
    {
        walkAudioTimer = 0.0f;
        runAudioTimer = 0.0f;
    }
}
 
void  SetSpeed (){
    float speed= walkSpeed;
 
    if ( chCtrl.isGrounded && Input.GetKey("left shift") || Input.GetKey("right shift") )
    {
        speed = runSpeed;
    }
 
    chMotor.movement.maxForwardSpeed = speed;
}
 
void  PlayFootsteps (){
    if ((Input.GetAxis( "Horizontal" )>0) || (Input.GetAxis( "Vertical" )>0) )
    {
       if ( Input.GetKey( "left shift" ) || Input.GetKey( "right shift" ) )
       {
         // Running
         isWalking = false;
         isRunning = true;
       }
       else
       {
         // Walking
         isWalking = true;
         isRunning = false;
       }
    }
    else
    {
       // Stopped
       isWalking = false;
       isRunning = false;
    }
 
    // Play Audio
    if ( isWalking )
    {
       if ( audio.clip != walk )
       {
         audio.Stop();
         audio.clip = walk;
       }
 
       //if ( !audio.isPlaying )
       if ( walkAudioTimer > walkAudioSpeed )
       {
         audio.Stop();
         audio.Play();
         walkAudioTimer = 0.0f;
       }
    }
    else if ( isRunning )
    {
       if ( audio.clip != run )
       {
         audio.Stop();
         audio.clip = run;
       }
 
       //if ( !audio.isPlaying )
       if ( runAudioTimer > runAudioSpeed )
       {
         audio.Stop();
         audio.Play();
         runAudioTimer = 0.0f;
       }
    }
    else
    {
       audio.Stop();
    }
 
    // increment timers
    walkAudioTimer += Time.deltaTime;
    runAudioTimer += Time.deltaTime;    
	}
}

Unity does allow some interaction between C# and JS files, but it’s very limited. Unity compiles your scripts in several stages. One script can “see” the other if it’s compiled in an earlier stage. You can find a list of compilation stages here.

If this is your only cross-language dependency, you can probably just move WalkingSoundScript out of Standard Assets.

If you have a lot of dependencies, things can get ugly. I try to stick to one language for a project.