Hurray!!!No,the link you gave is for prewired LEDs.Look at the heatshrink on the red wire.The resistor has already been fitted.
Dear Nigel (@NMBROOK),
That is exactly theanswer which I was waiting since I raised the question: some leds are pre-wired with resistors!
Thank you. Now everything is clear. I was just sick as all resources on Wen start to teach me the Ohm's law instead of explaining this simple idea. haha
OK, now I know what to do.