Why does this code have an output of 8? var z=0; for (var x=0;x<4;x++) { z+=2; } document.write(z);

Answer 1

0 + 2 = 2 (First loop) / 2* + 2 = 4 (2nd loop) / 4* + 2 = 6 (3rd loop) / 6* + 2 = 8 (4th loop) . The first value in the expression is carried from the earlier loop (the ones with asterisk).

Answer 2

x=0 z=2 ,x=1 z=4 , x=2 z=6 , x=3 z= 8

Answer 3

x starts at 0 and increments by 1 until it reaches 4 each time 2 is added to z thats 4 times which is 8

Answer 4

x=0 <4 true 》 z=z+2=0+2=2 》x=x+1=0+1=1 》
x=1 <4 true 》 z=z+2=2+2=4 》×=x+1=1+1=2 》
x=2 <4 true 》 z=z+2=4+2=6 》x=×+1=2+1=3 》
x=3 <4 true 》 z=z+2=6+2=8 》x=x+1=3+1=4 》
x=4 <4 false 》stop loop 》z=8

Answer 5

Answer to Namita question about z = 6:

You are right, last loop will execute with a value of x = 3, then x will increase (3 + 1 = 4) and loop will stop. But loop will start with a value of x = 0 (1st loop), then with x = 1 (2nd loop), then with x = 2 (3rd loop) and final loop with x = 3 (4th loop). And z = 8 in result.

Answer 6

The loop runs for x=0,1,2,3 and each time adds 2 to z. 4*2=8

Answer 7

we can give each loop a certain name...the first one, namely, zero loop, and so on...you 'll see we can only reach to forth one, namely, third loop...so we have to add 2 to the zero four times...

Answer 8

the statement "x++" means that x will be in incremented at the end of the statement the code is executing. In this case that statement is the entire loop, so x is not equal to 4 untill after Z is set to 8

Answer 9

That makes more sense now! I still have a question... if the condition is "x<4" how will the code continue for when x is equal to 4? Wouldn't it stop at x = 3.... making z=6?

Answer 10

yes it stops at 3 and then it add 1 to 3

Answer 11

your loop starts at 0, so 4 loops is 0 1 2 3.

Answer 12

yes final loop finishes at x=3..but then, to finsh the rest of the code, the (z+=2) gets executed once more thus making z=8. then it comes out of for loop..

Answer 13

thank they

Answer 14

x=0,z=0+2=2;x=1,z=2+2=4;x=2,z=4+2=6;x=3,z=6+2=8;x=4 condition false cntrol come out of loop

Answer 15

when x=0,z=2 and when x=1,z=4, and when x=2,z=6 and finally when x=3,z=8

Answer 16

Because you have used for loop for x till it gets value as 4 and z += 2 makes z double of x in the count.

Answer 17

It's simply because it's looping four times and each time it loops z is added to its self plus two. the last time it loops it is 6 + 2

Answer 18

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Answer 20

Hey guys Everyone explained the code great but uhh, what is the x++ doing in the entire loop? it's basically z=0 then it's put through the (for loop) where the first var x=0 is saying, the loop has.. looped 0 timezone and then the x <4; is saying you want the loop to repeat 4 times. and the z+=2 is saying you want (var z) to get an addition 2 every time your code loops. so 4*2=8. But.. what's the x++ for?? and also why is it z+=2 and not z=+2?