Javascript Types

Posted on by binarybuggs

Equality

  • Loose (non-)equality
  • Checks for value equality with implicit coercion (coercion algorithm depends on types)
  • One or both values are coerced (until the two types match) using a complex decision tree
  • Strict (non-)equality
  • Checks for both value and type equality (no coercion)

Type Conversion

Explicit coercion: controlled way of type conversion
Using complex primitive type constructors: String ( ) ,
Number ( ) , Date ( )

Implicit coercion: made by Javascript automatically
Writing to console: console . log (12 + HUF”) ;

Calling a method in a primitive type (like indexOf()), it’s
converted to its complex primitive type automatically

Performing loose equality check: 12 == “12”

Using unary operators: +sVar, ! ! svar

Overloading the OR operator

var sLocaIName = sName || “”:

if sName is null or undefined (coerced to false), an empty string will

be assigned to the variable. Otherwise, the value of

sName will be assigned 

<!DOCTYPE html >
<html>
   <head>
      <meta http-equiv="X-UA-Compatible" content="IE=edge">
      <meta charset="utf-8">
      <title>JS Basics - Equality</title>

      <script>
            var a = 1;
			var b = "1";
			
            console.log( "a == b: " + (a == b) );
            console.log( "a === b: " + (a === b) );
            
            function checkTruth(variable) {
            	if(variable) {
	            	console.log( "'" + variable + "' is true" );
	            } else {
	            	console.log( "'" + variable + "' is false" );
	            }
            }
            
            checkTruth(a);
            checkTruth("Text");

            checkTruth(0);
            checkTruth(-0);
            checkTruth(NaN);
            checkTruth("");
            checkTruth(null);
            checkTruth(undefined);
            checkTruth(false);
            
            //Coercion to string
            var iString = 1;
            new String(1);
            1+"";
            
            //Coercion to number
            var sNum = "1";
            new Number(sNum);
            +sNum;
            
            //Coercion to boolean
            var sBoolean = "Hello";
            new Boolean(sBoolean);
            !!sBoolean;
            
            //Overloading the OR operator
            function setName(sName) {
            	this.sLocalName = sName || "";
            	console.log(this.sLocalName);
            }
            setName();
            setName("World");
           
      </script>
   </head>
   <body class="sapUiBody" id="content">
   </body>
</html>

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