Arduino LED flashes with one button press
Because the digital writes only apply on if (digitalRead(button)==HIGH). If you don't press the button, then the code goes:

void loop() {
}


Essentially doing nothing. Your code needs a bit more to keep track of the button press. Pseudo Code:

if button == pressed {
    int tracker=1;
}
if tracker == 1 {
    led on;
    wait;
    led off;
    wait;
}
loop