Javascript to convert string to number?

问题:

var str = '0.25';

How to convert the above to 0.25?

回答1:

There are several ways to achieve it:

Using the unary plus operator:

var n = +str;

The Number constructor:

var n = Number(str);

The parseFloat function:

var n = parseFloat(str);

回答2:

var num = Number(str);

回答3:

var f = parseFloat(str);

回答4:

For your case, just use:

var str = '0.25';
var num = +str;

There are some ways to convert string to number in javascript.

The best way:

var num = +str;

It's simple enough and work with both int and float
num will be NaN if the str cannot be parsed to a valid number

You also can:

var num = Number(str); //without new. work with both int and float

or

var num = parseInt(str,10); //for integer number
var num = parseFloat(str); //for float number

DO NOT:

var num = new Number(str); //num will be an object. (typeof num == 'object') will be true.

Use parseInt only for special case, for example

var str = "ff";
var num = parseInt(str,16); //255

var str = "0xff";
var num = parseInt(str); //255