How to convert a string to a number in JavaScript

This article describes the method of digital spin string and string-spin in JavaScript

The simplest way to spin a digital string in JavaScript is to:

var num = 123;

var string = num + "";

That is, add a null character after the number. What about the simplest method of string-spin?

Strings can only be additive (stitching)

string addition (stitching) is very common, but the string for subtraction, multiplication, division?

This seems to be difficult to define, in fact, there is no subtraction, multiplication, division operation of Strings.

But JavaScript is a dynamic language, and if you take these three actions with two strings, he will try to turn them into numbers and then do the appropriate action. For example:

Alert ("45"-"32"); 13

Alert ("5" * "6"); 30

Alert ("12"/"3"); 4

But this conversion operation is not much like parseint and parsefloat, and it is similar to number, for example:

Alert ("123a"-"2BC"); NaN

Alert (parseint ("123a")-parseint ("2BC")); 121

Alert (Number ("123a")-Number ("2BC")); NaN

That is, this conversion, like number, converts the impure numeric string to Nan, indicating that it is a non-numeric.

And parseint, Parsefloat takes out the string to take out the front can be expressed as a number of parts, and ignore the following can not be expressed as a number of parts.