There's a new Node.js module for the MCP9808 temperature sensor at mcp9808-temperature-sensor. In addition to providing the ability to read the temperature this module goes the extra mile and can also be used to efficiently detect alerts with real hardware interrupts.
Here are some additional Node.js modules that you may find interesting
onoff - GPIO access and interrupt detection with Node.js
pigpio - Fast GPIO, PWM, servo control, state change notification and interrupt handling with Node.js on the Raspberry Pi
i2c-bus - I2C serial bus access with Node.js
spi-device - SPI serial bus access with Node.js
mcp-spi-adc - MCP3002/4/8, MCP3202/4/8 and MCP3304 SPI analog to digital conversion with Node.js