ES6 RegExp multiline

var re = new RegExp( "string" );
if ( re.multiline ){
   console.log("Test1-multiline property is set");  
} else {
   console.log("Test1-multiline property is not set");  
}
re = new RegExp( "string", "m" );

if ( re.multiline ){
   console.log("Test2-multiline property is set");  
} else {
   console.log("Test2-multiline property is not set");  
}