delete

delete

(), :

delete object.property
delete object['property']
delete object[index]
delete property //    , ,
                //   with,  ,    

(), delete .

object

, .

property

.

index

, , .

false, , , . true.

delete , . , , .

delete . . ( var) , , ( x = 5). .

delete ( Object, Array, Math ). ECMA-262 DontDelete.

x = 42; //   x   
var y = 43; //   , y
myobj = {};
myobj.h = 4; //   h  myobj
myobj.k = 5; //   k  myobj

delete x; //  true  (x -       )
delete y; //  false (delete     )
delete Math.PI; //  false (delete      )
delete myobj.h; //  true  (,     )

with (myobj) {
  delete k; //  true  ( delete myobj.k)
}

delete myobj; //  true  (myobj    ,  ,    )

, . .

function Foo() {}
Foo.prototype.bar = 42;
var foo = new Foo();
delete foo.bar; //  true,  ,   bar -  
alert(foo.bar); //  42,    
delete Foo.prototype.bar; //    
alert(foo.bar); //  "undefined",    

delete , . , a[3], a[4] a[4], a[3] . (delete a[a.length-1]).

delete , . , trees[3] delete.

const trees = ["redwood", "bay", "cedar", "oak", "maple"];
delete trees[3];
console.log(3 in trees); // false

, , undefined, undefined delete. , trees[3] undefined, :

const trees = ["redwood", "bay", "cedar", "oak", "maple"];
trees[3] = undefined;
console.log(3 in trees); // true

, ECMAScript , , , " " ( ). , Internet Explorer, - delete - , , , , . Internet Explorer, undefined, , - , , , .

, , ( ), .

• delete