How to disable jumping through a script?

You can also use the event UserInputService.JumpRequest.

-- disable jumping
Player.Character.Humanoid.JumpPower = 0
-- or
Player.Character.Humanoid:SetStateEnabled(Enum.HumanoidStateType.Jumping, false)
-- or
game:GetService("UserInputService").JumpRequest:Connect(function()
    Player.Character.Humanoid:SetStateEnabled(Enum.HumanoidStateType.Jumping, false)
end)

The most straight forward way is to set the player’s JumpPower to 0, or you can disable the humanoid’s jump state.

--to disable
player.Character.Humanoid.JumpPower = 0
--or
player.Character.Humanoid:SetStateEnabled(Enum.HumanoidStateType.Jumping, false)

--to enable
player.Character.Humanoid.JumpPower = 50
--or
player.Character.Humanoid:SetStateEnabled(Enum.HumanoidStateType.Jumping, true)

The easiest way to do this is to set your JumpPower to 0. You can do this from a script:

Player.Character.Humanoid.JumpPower = 0