Created
September 30, 2016 17:30
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Simple knock/tap detector
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| <html> | |
| <body> | |
| <script> | |
| const state = { | |
| x: 0, | |
| y: 0, | |
| z: 0, | |
| knocked: 0, | |
| }; | |
| const WINDOW_SIZE_MS = 500; | |
| const KNOCK_THRESHOLD_MS = 500; | |
| let framesPerWindow = 0; | |
| let frames = 0; | |
| window.ondevicemotion = function(event) { | |
| let {x, y, z} = event.acceleration; | |
| x = x === NaN ? 0 : x; | |
| y = y === NaN ? 0 : y; | |
| z = z === NaN ? 0 : z; | |
| framesPerWindow = WINDOW_SIZE_MS / event.interval; | |
| if (frames < framesPerWindow) { | |
| frames++; | |
| } | |
| state.x = (((frames - 1) * state.x) + x) / frames | |
| state.y = (((frames - 1) * state.y) + y) / frames | |
| state.z = (((frames - 1) * state.z) + z) / frames | |
| if (frames >= framesPerWindow) { | |
| if ( | |
| x > (state.x + 0.8) || | |
| y > (state.y + 0.8) || | |
| z > (state.z + 0.8) | |
| ) { | |
| state.knocked++; | |
| } | |
| if (state.knocked === 1) { | |
| state.firstKnock = Date.now(); | |
| } | |
| if (state.firstKnock) { | |
| if ((Date.now() - state.firstKnock) > KNOCK_THRESHOLD_MS) { | |
| console.log(state.knocked); | |
| if (state.knocked >= 2 && state.knocked < 9) { | |
| const pEl = document.createElement('p'); | |
| pEl.innerText = "Knocked!"; | |
| document.body.appendChild(pEl); | |
| } | |
| state.knocked = 0; | |
| state.firstKnock = false; | |
| } | |
| } | |
| } | |
| }; | |
| </script> | |
| </body> | |
| </html> |
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