Global Object

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

<<-JS Date Object -- JSON syntax in JavaScript->>

Daily Test with Code Example

HTML

CSS

JavaScript

PHP-MySQL

Which tag is used to add lists into <ul> and <ol> elements?

<ul>
 <li>http://coursesweb.net/html/</li>
 <li>http://coursesweb.net/css/</li>
</ul>

Which value of the "display" property creates a block box for the content and ads a bullet marker?

block list-item inline-block

.some_class {
  display: list-item;
}

Which instruction converts a JavaScript object into a JSON string.

JSON.parse() JSON.stringify eval()

var obj = {
 "courses": ["php", "javascript", "ajax"]
};
var jsonstr = JSON.stringify(obj);
alert(jsonstr);    // {"courses":["php","javascript","ajax"]}

Indicate the PHP class used to work with HTML and XML content in PHP.

stdClass PDO DOMDocument

$strhtml = '<body><div id="dv1">CoursesWeb.net</div></body>';
$dochtml = new DOMDocument();
$dochtml->loadHTML($strhtml);
$elm = $dochtml->getElementById("dv1");
echo $elm->nodeValue;    // CoursesWeb.net