在JavaScript中将float转换为32位十六进制字符串

Question

I have a float value representing gps coordinates and I liked to convert it to a 32bit hex string.

I tried every solution described here but everytime, the result is not what I am expecting.

For example, most of the 'ToHex' functions :

var lat = 45.839152;
console.log(ToHex(lat));

returns me '2d.56d0b30b5aa8'

but I am expecting '42355b43' for result as most converters returns

do you know how I could get '42355b43' as a result in JavaScript ?

Thank you !

Answer 1

You could take the TypedArray object with an ArrayBuffer and DataView .

Then set the value as float 32 and read the view as unsigned integer 8 bit for the values.

 const getHex = i => ('00' + i.toString(16)).slice(-2); var view = new DataView(new ArrayBuffer(4)), result; view.setFloat32(0, 45.839152); result = Array .apply(null, { length: 4 }) .map((_, i) => getHex(view.getUint8(i))) .join(''); console.log(result); 

Answer 2

I finally decide to code my own function. I post it here so it could help people :

function ToHex(d) {

    var sign = "0";

    if(d<0.0){
        sign = "1";
        d = -d;
    }

    var mantissa = parseFloat(d).toString(2);

    var exponent = 0;

    if(mantissa.substr(0,1) === "0"){
        exponent = mantissa.indexOf('.') - mantissa.indexOf('1') + 127;
    }
    else{
        exponent = mantissa.indexOf('.') - 1 + 127;
    }

    mantissa = mantissa.replace(".", "");
    mantissa = mantissa.substr(mantissa.indexOf('1')+1);

    if(mantissa.length>23){
        mantissa = mantissa.substr(0,23);
    }
    else{
        while(mantissa.length<23){
            mantissa = mantissa +"0";
        }
    }

    var exp = parseFloat(exponent).toString(2);

    while(exp.length<8){
        exp = "0" + exp;
    }

    var numberFull = sign + exp + mantissa;

    return parseInt(numberFull, 2).toString(16);
}