[Learning] #16 JS: loop — Part 1

while statement

If the statement is true, the code inside of {} would be executed.
When the first execution is done, the system will return to the while to repeat the execution.
The loop will stop until the result becomes false.

var n=0;
while(n<=50) {
n++;
}
alert(n);

var sum=0;
var i=1;
while(i<=100){
sum=sum+i; → it can be written as sum+=i as well.
i++;
}
alert(sum);

for statement

  • The concept of while and for is similar, but for combines 3 important blocks together, which makes the code simpler.
  • Each of the statement means: for(initialization command;statement for decide whether the next loop continues;execute after every loop){
    }
var sum=0;
for(var i=1;i<=100;i++){
sum=sum+i;
}
alert(sum);

break & continue

  • break; → “jumps out” of a loop (強制跳出迴圈)
  • continue; → “jumps over” one iteration in the loop (強制進行下一次的迴圈)
    by W3C Schools

Example 1. while statement x break

var n=0
while(n<=100){
if(n==50){
break;
}
n++;
}
alert(n);

=>n is 50.

Example 2. for statement x continue

var x=0;
for(var n=0;n<=100;n++){
if(n%4==0){ → n can be divided exactly by 4.
continue;
}
x++;
}
alert(x);

=>x is 75.

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Vida Lin

Vida Lin

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