1. How to add properties to an object? Method 1: var b = {}; B/” name ”=” test ”; Delete b.ame deletes the properties of the object Method 2: b.ame =“test”; **2. How to determine whether a variable is declared or not? **Typeof (a) = = “undefined” Typeof (d) == whether “function” is a function

3. How is it represented as a string? Through double quotes (""), single line (""), backslash (//)     “1 + 1 = 11.     1 + ‘1’ = 11 There is only one number type in Javascript, and that is number. 5. Basic data types for Javascript? Number, string, Boolean, undefined, Null Also: Object

6. What is the difference between a class and an object? How do I implement this in javascript?

function myClass()
{ }
myClass.prototype.ID = 1;
myClass.prototype.Name = "johnson";
myClass.prototype.showMessage = function()
{
    alert("ID: " + this.ID + "Name: " + this.Name);
}
var obj1 = new myClass();
obj1.showMessage();

7. How many different types of loops are there in JavaScript? Two kinds. For loop and while loop.