Global Object

Javascript Course

• Methods of the Global object

The Global object has properties and methods at the highest level, without a parent object. This means the global properties and functions can be used with all the built-in JavaScript objects.

Properties of the Global object

• Infinity - A numeric value that represents positive/negative infinity

  var xn = 1.8976543348623157E+12088;
  document.write(xn); // Infinity
  

• NaN - 'Not-a-Number', represents an object that is not a valid number

  var minutes = 61;
  
  if(minutes<0 || minutes>60) {
   minutes = Number.NaN;
  }
  
  document.write(minutes); // NaN
  

• undefined - Indicates that a variable has not been assigned a value

  var xv;
  if(xv==undefined) {
   document.write('xv is undefined');
  }
  

Methods of the Global object

• escape('str') - Encodes the non alpha-numeric characters from a string ('str')

  var str = 'ab @# 78';
  document.write(escape(str)); // ab%20@%23%2078
  

• eval('str_code') - Evaluates a string and executes it as if it was script code

  let str ="document.write('coursesweb.net');";
  eval(str); // coursesweb.net
  

• isFinite(nr) - Returns true if 'nr' is a finite, legal number, otherwise false

  document.write(isFinite(123) +'<br>'); // true
  document.write(isFinite('string')); // false
  

• isNaN(nr) - Returns true if 'nr' is an illegal number, otherwise false

  document.write(isNaN(123) +'<br>'); // false
  document.write(isNaN('string')); // true
  

• Number(obj) - Converts an object's value to a number

  var dat = new Date();
  document.write(Number(dat) +'<br>'); // 1296464847762
  document.write(Number('0078')); // 78
  

• parseFloat('str') - Transforms a string into a floating point number

  document.write(parseFloat('12.8 pm')); // 12.8
  

• parseInt('str') - Transforms a string into an integer number

  document.write(parseInt('12.8 pm')); // 12
  

• String(obj) - Converts an object's value to a string

  var dat = new Date();
  document.write(String(dat)); // Mon Jan 31 2011 11:13:47 GMT+0200 (GTB Standard Time)
  

• unescape('str') - Decodes a string encoded with escape().

  var str = 'ab%20@%23%2078';
  document.write(unescape(str)); // ab @# 78