concept digital input in category javascript

This is an excerpt from Manning's book JavaScript on Things: Hacking hardware for web developers. Login to get full access to this book.

Figure 4.2. An analog sensor like a temperature sensor (top) transduces changes in temperature into a smooth, analog signal. A digital input like a tilt switch (bottom) might have as few as two discrete output values: one when oriented normally (off, LOW, 0, or false) and one when inverted (on, HIGH, 1, true).

Using a pull-down resistor is one way to avoid a floating situation of indeterminate logic level when digital inputs are disconnected or inactive.