从String到float的奇怪转换

Question

I have a webview with javascript-interface.

From within this webview i do certain javascript operations.

In one of those i set an onclick attribute for one of the elements in my webcontent. ( using jquery)

button.attr("onclick", "Android.doStuff(".concat(stringContainingOnlyNumbers).concat(")"));

As you might guess the variable stringContainingOnlyNumbers holds a String containing only numbers.

Android is the keyword for my javascript-interface.

If i click the button i manipulated the method doStuff is gettin called on the interface.

Everything fine so far.

But what the String Parameter holding looks like a float value.

So what looks like this on js side:

1344810353

Comes out on my interface like this:

1.34447e+09

Can anyone help me out here and explain why this conversion happens?

Answer 1

That isn't really a conversion, it's just rewriting it to fewer decimal digits using scientific notation.
1344810353 rounded to 6 digits is 1.34447e+09, which btw is 1.34447 * 10^9.

It's a float, and javascript tends to shorten numbers when concatenating them as strings.
Here's an example: http://jsfiddle.net/YGC8B/

You can fix this by iterating through the numbers digits and displaying them one by one.

function getString(number) {
    var numstring = "";
    var num = number;
    while (num > 0) {
        numstring = num % 10 + numstring;
        num -= num % 10;
        num /= 10;
    }
    return numstring;
}
var number = 1344810353;
log(getString(number)); // or however your output it

Here's a working example: http://jsfiddle.net/Tj5Zy/


A side note:

It's best not to use the attribute of an element, it's slightly deprecated. I would recommend attaching the event.
And since you're using jQuery, it's just all the easier.

button.bind('click',function() {
    Android.doStuff(stringContainingOnlyNumbers);
});

Answer 2

What is happening there is not a conversion to float, but you are getting a scientific notation for that integer. It must be happening in concat. Can't you do something like:

button.attr("onclick", "Android.doStuff(" + stringContainingOnlyNumbers + ")");

?