setAttribute troubles

[qszhc123]

there is a <input type="hidden" id="test1"> in my page, and i want to use JS to give it a long string consisting of numbers,which is like  "454544878545455487",

when some button(<input type="button" onclick="testFunc();">) is clicked.

The testFunc is like followings:

<script type="text/javascript">

  function testFunc()

  {

    document.getElementById("test1").setAttribute("value",somestring);

    XXXX.submit();

  }

</script>

 

when the somestring is short,such as "12345678",that's ok,

but when it is long,for example,"454544878545455487", the value appears like 4.54544878545455e+17 ,

so i add a .toString() ,

document.getElementById("test1").setAttribute("value",somestring.toString());

it is now a strange string like "454544878545455500"

approximately, but doesn't equal to "454544878545455487"...

 

VERY LATE NOW,  AND THANKS VERY MUCH ~~

[Adam]

You're not declaring it a string like you think, it's a number. What you're seeing (4.54544878545455e+17) is scientific E notation. JavaScript does this so it can represent numbers larger than it's internally physically capable of storing. Your number exceeds that maximum, so you're loosing some bits off the end and it's being rounded.

 

You can see the cut off point here:

 

var num1 = 9007199254740992;
var num2 = 9007199254740993;

if (num1 == num2) {
    // true
}

 

If you only want a string, just define it wrapped in quotes and you won't have a problem. If you don't, things get more complicated, but I'll wait and find out before spending the time typing it up!

[qszhc123]

Thanks a lot~~

 

it's obvious that i should use '  ', and i just made a simple mistake!