问题:

I searched and only found this one related to my question, but not exactly the same, as I'm using toFixed rather than toPrecision. Why does toPrecision return a String?

Here is my code

var oldv = parseFloat(document.getElementById('total').textContent).toFixed(2);
alert(typeof oldv); // returns string
var testv = parseInt(document.getElementById('total').textContent);
alert(typeof testv); // returns number

I need further math steps, so string type messed up... Why? How to solve? TIA

回答1:

As mentioned in docs, toFixed returns

A string representing the given number using fixed-point notation

In case you need to use the returned result as a number, you can use built-in object Number:

var oldv = parseFloat(Math.PI).toFixed(2);

console.log( oldv );
console.log( typeof oldv ); // returns string

var num = Number(oldv);
console.log( num );
console.log( typeof num );  // returns number

回答2:

The Number.prototype.toFixed() function is supposed to return a string type as per the documentation found here.

If you need to perform further arithmetic with the number you can coerce it back into numeric form using the Unary plus operator before the variable name (+) documented here like so:

var oldv = parseFloat(document.getElementById('total').textContent).toFixed(2);

alert(typeof oldv); // Returns string

alert(typeof +oldv); // Returns number