在Javascript中将字符串转换为负浮点数

Question

The negative numeric value I'm getting from the back-end application is formatted according to our internal configuration (UI user profile). In other words, for value -23.79879 my xml input may be <myNumber>-23.79879</myNumber> or <myNumber>23,79879-</myNumber> or other
and I can't turn the formatting off.
The assumption is that the formats are "standard", normally used for localization.
I'm looking to do something like:

convertStringToNumber(numberString, formatString, slignPosition)

Answer 1

Not sure what you mean with formatString, but maybe something like this?:

function convertStringToNumber(num){
    num=num.split(',').join('.');
    if(num.indexOf('-') ==num.length-1){
        num='-'+num.substr(0,num.length-1);
    }
    return parseFloat(num) || null;
}



console.log(convertStringToNumber("-23.79879"))
console.log(convertStringToNumber("23,79879-"))

Answer 2

The easiest way to achieve this is to expose the parsing rule from the backend, which obviously knows the format. This can be done in many ways, but one easy way i am fond of is simply to break down all the moving parts of the format, define properties for each on an object and then expose that object to the parser.

The object could look something like this:

var opts =  {
  thousandsSeparator: ',',
  decimalSeparator: '.',
  negativeSign: '-'
};

Then pass that object into a parsing function like this:

function parseNumber(opts, str) {
      var isNegative = false;
        if(str.indexOf(opts.negativeSign) != -1) {
            isNegative = true;
            str = str.replace(opts.negativeSign,'');
        }
        var parts = str.split(opts.thousandsSeparator).join('').split(opts.decimalSeparator);
        var num = 1 * parts[0];
        var deci = 1 * parts[1];
        if(deci) num += deci /  Math.pow(10,parts[1].length);
        return isNegative ? -1 * num : num;
}

You would then call it like thuis:

parseNumber(opts,'2,345.234-'); //-2345.234