js method to delete a field in an object

// The following method does not change the original object let item = {
    name:'Zhang San',
    age:'18',
    gender:'male'
   };
   console.log(item) // {age: "18",gender: "male",name: "Zhang San"}


   let { age,...params } = item;
   console.log(item) // {age: "18",gender: "male",name: "Zhang San"}
   console.log(typeof params.age) // undefined
   console.log(params) // {gender: "男",name: "张三"}

   // The following methods will directly change the object let item1 = {
    name:'Zhang San',
    age:'18',
    gender:'male'
   };
   console.log(item1) // {age: "18",gender: "male",name: "Zhang San"}
   delete item1.name;
   console.log(typeof item1.name) // undefined
   console.log(item1) // // {age: "18",gender: "male"}

var Employee = {
 age: 28,
 name: 'abc',
 designation: 'developer'
}

console.log(delete Employee.name); // returns true
console.log(delete Employee.age); // returns true

// When trying to delete a non-existent attribute // This will also return true
console.log(delete Employee.salary); // returns true

var Employee = {};
Object.defineProperty(Employee, 'name', {configurable: false});

console.log(delete Employee.name); // returns false

var nameOther = 'XYZ';

// Get global properties through the following methods:
Object.getOwnPropertyDescriptor(window, 'nameOther');

// Output: Object {value: "XYZ",
// writable: true,
// enumerable: true,
// configurable: false}

// Because "nameOther" is added using the var keyword,
// It is set to non-configurable
delete nameOther; // return false

Object.defineProperty(globalThis, 'variable1', { value: 10, configurable: true, });
Object.defineProperty(globalThis, 'variable2', { value: 10, configurable: false, });

console.log(delete variable1); // true

// SyntaxError in strict mode.
console.log(delete variable2); // false

function func(param) {
 // SyntaxError in strict mode.
 console.log(delete param); // false
}

// SyntaxError in strict mode.
console.log(delete func); // false

function Employee() {
 delete salary;
 var salary;
}

Employee();

function Employee() {
 delete salary; // SyntaxError
 var salary;
}

// Similarly, any direct use of the delete operator on any function // will throw a syntax error.

function DemoFunction() {
 //some code
}

delete DemoFunction; // SyntaxError

// Create adminName attribute in global scope adminName = 'xyz';

// Create the empCount property in the global scope // Because we used var, it will be marked as non-configurable. Likewise let or const are not configurable.
var empCount = 43;

EmployeeDetails = {
 name: 'xyz',
 age: 5,
 designation: 'Developer'
};

// adminName is a property of the global scope.
// Because it is not created with var, it can be deleted.
// Therefore, it is configurable.
delete adminName; // returns true

// In contrast, empCount is not configurable.
// because var was used when creating it.
delete empCount; // returns false

// delete can be used to delete the attributes of an object delete EmployeeDetails.name; // returns true

// Even if the property does not exist, it will return "true"
delete EmployeeDetails.salary; // returns true

// delete has no effect on built-in static properties delete Math.PI; // returns false

// EmployeeDetails is a property of the global scope.
// Because it is defined without "var", it is marked as configurable.
delete EmployeeDetails; // returns true

function f() {
 var z = 44;

 // delete has no effect on local variable names delete z; // returns false
}

function Foo() {
 this.bar = 10;
}

Foo.prototype.bar = 42;

var foo = new Foo();

// Returns true because the property deleted is the foo object's own property delete foo.bar;

// foo.bar is still available because it is available on the prototype chain.
console.log(foo.bar); //42

// Delete the property from the prototype delete Foo.prototype.bar; //true

// Since the "bar" property has been removed, it can no longer be inherited from Foo.
console.log(foo.bar); //undefined

var trees = ["redwood","bay","cedar","oak","maple"];
delete trees[3];
if (3 in trees) {
  // This will not be executed}

var trees = ["redwood","bay","cedar","oak","maple"];
trees[3] = undefined;
if (3 in trees) {
  // This will be executed}

var trees = ['redwood', 'bay', 'cedar', 'oak', 'maple'];
trees.splice(3,1);
console.log(trees); // ["redwood", "bay", "cedar", "maple"]