Javascript casts floating point numbers to integers without cause

问题

I wrote a function that behaves differently depending on the numeric type of it's parameters. Integer or float.

Using some code from this question How do I check that a number is float or integer? it was easy to detect if float or not but then I stumbled upon the case that javascript casts 1.0 to 1 without cause if you call a function using that number.

Example:

function dump(a, b) {
 console.log(a, typeof b, b);
}

dump('1', 1);
dump('1.0', 1.0);
dump('1.1', 1.1);

Output chrome, firefox, ie, opera and safari all gave the same result:

1   number 1
1.0 number 1 "wrong"
1.1 number 1.1

I know that javascript only knows the type number but that forced cast seems to go way overboard. The only solution I came up with was to call the function using string values like '1.0', detect the dot and use parseFloat or parseInt.

Any suggestion on that?

回答1:

You've acknowledged that JavaScript only has a single Number type. As such, 1 is identical to 1.0.

If you need this for display purposes, then you should use toFixed.

1..toFixed(1); // "1.0"

回答2:

number%1===0 

If that condition is true , it's integer, else it's float

来源：https://stackoverflow.com/questions/11798903/javascript-casts-floating-point-numbers-to-integers-without-cause