An example showing how to use a 4051 multiplexer with an esp8266 to connect up to 8 analog sensors.
Buy the Multiplexers here:
Buy the ESP8266 here:
D4 -> S0 (A)
D3 -> S1 (B)
D2 -> S2 (C)
A0 -> Common
3.3v -> VCC
G -> GND
G -> Inhibit
G -> VEE