Jumping

Notes

Use the arrow keys to move the player left and right. Press the up arrow to jump.

Jumping is a combination of two things: an upward velocity and gravity. When the up arrow is pressed and the player is touching the ground, an upward velocity is added to the player. Gravity then accelerates the character back towards the ground. The parabolic path of the player while jumping is simply a result of the player being affected by gravity.

Source