JS Interview Basics

Problem:

What types of typeof can I get in 1.JS?

Test Center: JS Variable Type

2. When to use double equals = =? When to use the third-level = = =?

Test Center: Forced type conversion

The difference between 3.window.onload and domcontentloaded.

4. Use JS to create 10 <a> tags, click the time to bounce out the corresponding serial number.

Test Centers: Scopes

5. A brief description of how to implement a module loader to achieve basic functionality similar to Require.js.

Test Center: JS Modular

6. Implementing random ordering of arrays

Test Center: JS's basic algorithm.

1. Variables are divided into value types and reference types.

var a = 100;

var B = A;

A = 200;

Console.log (b); The print out is 100;

var a = {age:20};

var B = A;

B.age = 21;

Console.log (A.age); It's 21 printed.

Object array functions are reference types

typeof undefined//undefined;

typeof "AB"//string

typeof 123//number

typeof Ture//boolean

typeof can be distinguished for value types

typeof {}//object

typeof []//object

typeof null//object A null pointer does not point to any object

typeof Console.log//function

typeof distinguishes a value type but cannot differentiate between reference types, except for functions that are not distinguished, but that are objects of type object type, and that reference types can have unrestricted extended properties

2. Forcing type conversions

string concatenation = = (double equals) operator If statement logical operation is a type that can be coerced.

var a = 100 + 10;

Console.log (a); Type of

var b = 100 + "10";

Console.log (b); "10010" string type, because the + number, did a lightweight type conversion, the number into a string, and then connected together.

"//true";

0 = = ""//true; Empty string

Null = = undefined//true; Both null and undefined two can themselves be converted to false, so they can be equal.

JS Interview Basics