THE FULLY WORKING ONE

const byte button=2;
const byte LED=10;
bool blinking =false; unsigned long blinkInterval=250;
unsigned long currentMillis;
unsigned long previousMillis;
void setup() { pinMode(button,INPUT); pinMode(LED,OUTPUT); } void loop() {

if(blinking) {
    currentMillis =millis();

    unsigned long blinkInterval=100;
    if((unsigned long)(currentMillis-previousMillis) >= blinkInterval) { 
        digitalWrite(LED,!digitalRead(LED)); LED
        previousMillis =currentMillis;
    }
} else {
    digitalWrite(LED,LOW); 
}

int reading=digitalRead(button);
delay(100); 

if(reading==LOW) 
{ blinking =true; }
else
{ blinking =false; }

}

The fully working sketch

const byte button=2;                     
const byte LED=10;                 
bool blinking =false;
unsigned long blinkInterval=250;                      
unsigned long currentMillis;                        
unsigned long previousMillis;                       
void setup()
{
    pinMode(button,INPUT);
    pinMode(LED,OUTPUT);
}
void loop()
{
   
    if(blinking) {
        currentMillis =millis();

        unsigned long blinkInterval=100;
        if((unsigned long)(currentMillis-previousMillis) >= blinkInterval) { 
            digitalWrite(LED,!digitalRead(LED)); LED
            previousMillis =currentMillis;
        }
    } else {
        digitalWrite(LED,LOW); 
    }

    int reading=digitalRead(button);
    delay(100); 

    if(reading==LOW) 
    { blinking =true; }
    else
    { blinking =false; }
}

const byte button=2; const byte LED=10; bool blinking =false;//defines when blinking should occur unsigned long blinkInterval=250;// number of milliseconds for blink unsigned long currentMillis;// variables to track millis() unsigned long previousMillis; void setup() { pinMode(button,INPUT); pinMode(LED,OUTPUT); } void loop() { // this code blinks the LED if(blinking) { currentMillis =millis();// better to store in variable, for less jitter

    unsigned long blinkInterval=100;
    if((unsigned long)(currentMillis-previousMillis) >= blinkInterval) { 
        digitalWrite(LED,!digitalRead(LED)); // shortcut to toggle the LED
        previousMillis =currentMillis;// sets the time we wait "from"
    }
} else {
    digitalWrite(LED,LOW); // force LED off when not blinking
}

int reading=digitalRead(button);
delay(100); // crude de-bouncing

if(reading==LOW) // buttons with pull-up are pressed when LOW
{ blinking =true; }// start blinking
else
{ blinking =false; }// stop blinking

}

THE FULLY WORKING ONE

const byte button=2; 
const byte LED=10; 
bool blinking =false; unsigned long blinkInterval=250; 
unsigned long currentMillis; 
unsigned long previousMillis; 
void setup() { pinMode(button,INPUT); pinMode(LED,OUTPUT); } void loop() {

if(blinking) {
    currentMillis =millis();

    unsigned long blinkInterval=100;
    if((unsigned long)(currentMillis-previousMillis) >= blinkInterval) { 
        digitalWrite(LED,!digitalRead(LED)); LED
        previousMillis =currentMillis;
    }
} else {
    digitalWrite(LED,LOW); 
}

int reading=digitalRead(button);
delay(100); 

if(reading==LOW) 
{ blinking =true; }
else
{ blinking =false; }

}