Why can't I use toFixed on an HTML input object's value?

Question

I have an HTML input element and I\'m trying to force a single decimal place into the input after the user changes the value. So, let\'s say the user enters \"4\", I run th

Answer 1

convert to a Number first,

this.value = Number(this.value).toFixed(1);

this.value is a String, and a string does not have the toFixed method.

Answer 2

this.value is a String when you get it from an input element. You need to cast it to a number before you can use a number's methods on it:

this.value = Number(this.value).toFixed(1);

Alternatively you can use the unary + operator to cast the string to a number:

this.value (+this.value).toFixed(1);

If you need to remove string suffixes, then you could use parseFloat:

this.value = parseFloat(this.value).toFixed(1);

However, it's worth noting that parseFloat does not handle hexadecimal formats while casting to Number does:

this.value = +'0xF'; //15
this.value = parseFloat('0xF'); //0