#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 (强制跳出回圈)
• continue; → "jumps over" one iteration in the loop (强制进行下一次的回圈)
  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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