[JS] How to get a node existed/created in creator and move rigidbody?

Here’s what i’m trying to do.
I have a node mainChar in the nodetree on top left.
I have a node btn_left & btn_right.
I have a script movementControl.
And when i press my btn_left, i run the click events [0] with movementControl node, movementControl and moveLeft function.

How do i get the mainChar node from the script?
i tried using cc.find(“mainChar”),
then i tried using document.getElementById(“mainChar”)
then i tried using mainChar directly.

but i still can’t seems to get it to work.

And how do i move the rigidbody?
I’m using mainChar.getComponent(cc.RigidBody).linearVelocity = cc.p(350,0);
but i got error of “mainChar is not defined”. so i’m not sure if this will works or not yet.