javascript Error - for loop

Question

I wrote a this simple code in js.

    var n=10;
    for (i=1;i=n;i++){
    console.log('avinsyh');
     }

But the loop executes greater than 2000 and crashing the browser.Why this is happening so?

Note: If I Execute this:

 var n=10;
    for (i=1;i<n;i++){
    console.log('avinsyh');
     }

Then the javascritpt outputs the correct results

for (START, LIMIT, INCREMENT) you have for (START, START, INCREMENT) — Unamata Sanatarai
– Unamata Sanatarai, Commented Mar 31, 2016 at 7:16
A single equals sign (=) is assignment operator, you will need to use a double equals sign (==) which is the comparison operator, in the second part of the for loop — Valeklosse
– Valeklosse, Commented Mar 31, 2016 at 7:18
@Valeklosse Even if put (i == n ) the code is not executing also no error — Avinash
– Avinash, Commented Mar 31, 2016 at 7:51
@Avinash the code probably is executing, but because i (1) is not equal to n (10), it wont enter the loop, in effect the loop will only ever excute once in this manner. If you want it to run until i(1) == n(10), then best to use != or <= — Valeklosse
– Valeklosse, Commented Mar 31, 2016 at 11:38

Nina Scholz · Accepted Answer · 2016-03-31 07:59:12Z

4

It's the assignment in the comparison part of the for loop, which makes an infinite loop. i becomes always n and evaluates to true.

for (i = 1; i = n; i++){
//          ^^^^^

var n = 10,
    i;

for (i = 1; i <= n; i++){
    document.write('i: ' + i + '<br>');
}

edited Mar 31, 2016 at 7:59

answered Mar 31, 2016 at 7:13

Nina Scholz

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1 Comment

Nina Scholz Over a year ago

for (i=1; i < n; i++){ opposite.

Ramanlfc · Accepted Answer · 2016-03-31 07:13:16Z

2

in your first for loop , i=n will set i equal to the value of n and thus return a truthy value(as n is not 0) and you get a infinite loop.

answered Mar 31, 2016 at 7:13

Ramanlfc

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Comments

Rahul Tripathi · Accepted Answer · 2016-03-31 07:21:00Z

2

In your for loop you are assinging the value i = n which is always true and hence results in infinite loop.

The condition expression is evaluated. If the value of condition is true, the loop statements execute. If the value of condition is false, the for loop terminates. If the condition expression is omitted entirely, the condition is assumed to be true.

In your second case you are comparing the value of i on each iteration and hence you are getting the expected result.

The basic syntax of for loop is:

for ([initialExpression]; [condition]; [incrementExpression])  
 statement

So in your first case you are not providing the [condition] rather it is an assignment.

edited Mar 31, 2016 at 7:21

answered Mar 31, 2016 at 7:14

Rahul Tripathi

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