I would like to know how can I control the jump movement of a character in Unity3D. Basically I am trying to program the jump in such a way that while a jump is in progress the character is allowed to move either left or right in mid-air when the corresponding keys are pressed. With my script the character will correctly move to the left when, for example, the left key is pressed, but when the right key is pressed afterwards, the character moves to the right before the movement to the left is completed.

Following is the script:

void Update () {

if(touchingPlatform && Input.GetButtonDown("Jump")){
    rigidbody.AddForce(jumpVelocity, ForceMode.VelocityChange);
    touchingPlatform = false;
    isJump=true;
}

//left & right movement
Vector3 moveDir = Vector3.zero;
if(Input.GetKey ("right")||Input.GetKey ("left")){
    moveDir.x = Input.GetAxis("Horizontal"); // get result of AD keys in X

    if(ShipCurrentSpeed==0)
    {
        transform.position += moveDir * 3f * Time.deltaTime;
    }else if(ShipCurrentSpeed<=15)
    {
        transform.position += moveDir * ShipCurrentSpeed * 2f * Time.deltaTime;
    }else
    {
        transform.position += moveDir * 30f * Time.deltaTime;
    }
}