Object Number in JavaScript. Code examples

The Number object represents numbers. To create a number, you must pass a number or a string to the Number constructor, representing a number. Another way to assign a number to a variable:

var x = new Number(33);
var y = new Number('33');
document.write(x + y); // 66

Properties of the Number object

The Number object provides a number of properties and methods. Some of its properties:

• Number.MAX_VALUE – largest possible integer. Approximately equal to 1.79E+308. Numbers greater than this value are treated as Infinity
• Number.MIN_VALUE – the smallest possible positive integer. Approximately equal to 5e-324 (somewhere around zero)
• Number.NaN – a special value that indicates that the object is not a number
• Number.NEGATIVE_INFINITY – A value that denotes a negative uncertainty and that occurs when an overflow occurs.
• Number.POSITIVE_INFINITY – positive definiteness
• isNaN() – determines if an object is a number. If the object is not a number, then true is returned.

  var a = Number.isNaN(Number.NaN); // true
              var b = Number.isNaN(true); // false - new Number(true) = 1
              var c = Number.isNaN(null);  // false - new Number(null) = 0
              var d = Number.isNaN(25);  // false
              var e = Number.isNaN("54"); // false
  

• parseFloat() – converts a string to a floating point number. For example:

              var a = Number.parseFloat("34.90"); // 34.9
              document.write(a);
              var b = Number.parseFloat("hello"); // NaN
              document.write(b);
              var c = Number.parseFloat("34hello"); // 34
              document.write(c); 
  

• parseInt() – converts a string to an integer. For example:

    var a = Number.parseInt("34.90"); // 34
              document.write(a);
              var b = Number.parseInt("hello"); // NaN
              document.write(b);
              var c = Number.parseInt("25hello"); // 25
              document.write(c); 
  

• toFixed – wraps to a coma by a certain number of characters

  var a = 10 / 1.44;
          a = a.toFixed(2); // leave two decimal places