Join two numbers to create a new number composed of integer and decimal part

Question

I have two numbers and I need to convert them into a number composed of an integer part and a decimal part.

I'm having problems because the number that represents the integer part can be 0 or -0

I thought of something like that but the result still doesn't get the 0 sign. I thought of using Math.sign but it returns 0 if it's 0 or -0.

const i = -0
const f = 20

const value = parseFloat(i.toString() + "." + f.toString())

console.log(value)

Answer 1

in js this is expected

// Positive and negative zero are equal to each other in JavaScript:
console.log(+0 === -0) // true
console.log(+0 == -0) // true

// Note that +0 is the same as 0:
console.log(+0) // 0
console.log(0 === -0) // true
console.log(0 == -0) // true

This behavior comes from ECMAScript section 7.2.13

So to differentiate you should use Object.is: (ES6+)

console.log(+0 === -0) // true
console.log(Object.is(+0,-0)) // false


function makeN(i,f){
    return  (i + f / 100) * (Object.is(i,-0)?-1:1);
}

console.log(makeN(-0,20)); //-0.20
console.log(makeN(0,20)); //0.20

Using ES5 or below you can use -Infinity as 1/-0 produce -Infinity

console.log(1/-0) // -Infinity
console.log(1/-0 === -Infinity) // true

function makeN(i,f){
    return  (i + f / 100) * (1/i === -Infinity?-1:1);
}

console.log(makeN(-0,20)); //-0.20
console.log(makeN(0,20)); //0.20

A solution not limited to 2 decimal place Using jsbench.me, toString + parseFloat is like 93% slower than the following solution

function makeN(i,f){
    return  (i + f / (Math.pow(10,f.toString().length))) * (Object.is(i,-0)?-1:1);
}