JS Getting Started basics (if else and switch Case/node installation)

In JavaScript, to perform different actions for different decisions, we can use the following conditional statements:

• If statement-use this statement to execute code only if the specified condition is true
• If...else Statement-executes code when the condition is true and executes other code when the condition is false
• If...else If....else Statement-Use this statement to select one of several code blocks to execute
• Switch statement-Use this statement to select one of several code blocks to execute

Multiple judgments (if.. else nested statements)

if (condition 1) {condition 10% code to execute immediately} Else  if (condition 2) {condition 20% code executed immediately} ... Else  if (condition N) {The code executed when condition n was established} Else {conditions 1, 2 to n are not immediately executed code}

Case one:

Enter your name, height, weight, gender, and determine your physical condition, respectively. (weight per kilogram)

Calculation Formula man= weight-(height -100), woman= weight-(height-110); More than 3 is overweight, less than 3 is thin, the rest is normal

varReadline=require ('Readline-sync') Console.log ('Please enter your name')varName=readline.question (); Console.log ('Please enter your height')varheight=parseint (Readline.question ()); Console.log ('Please enter your weight')varweight=parseint (Readline.question ()); Console.log ('Please enter gender (Man/woman)')varsex=readline.question ();if(sex=='Mans'){    varmanhealth=weight-(height- -); if(manhealth>3) {Console.log ('Overweight')    }    Else if(manhealth<3) {Console.log ('Partial Thin')    }    Else{Console.log ('Health')    }}if(sex=='woman'){    varHealth=parseint (weight-(height- the)); if(health>3) {Console.log ('Overweight')    }    Else if(health<3) {Console.log ('Partial Thin')    }    Else{Console.log ('Health')    }}

Switch is more convenient than if else when there are a number of options.

Switch (expression) {  case value 1:1break, case  value 2:  2   break ;... case value N:  execute code block n  break; default :  code executed when the case value is 1, 2...case value n

break; The loop will end without outputting the contents of the back loop
Continue this cycle will be skipped, and subsequent loops will not be affected

To install the node step:

1.node Installation

Just a little bit, OK.

2. Modify the image address (download module)

NPM Conflig Set registry=https://registry.npm.taobao.org

(School LAN) server mirroring: Typing in the command line

NPM Config set registry=http://192.168.8.10:7001

3. See if the installation was successful: Node-v

4. Create folder, cmd to enter file

Enter NPM init initialization file and a Package.json file will be created after success

5. Create a ***.js file in the file that writes Console.log (' 111111 ')

6. Open with CMD, DOS command into folder, run NodeE * * * or node ***.js

Installing the Input module: NPM Install Readline-sync

Successful download will automatically generate a Node_modules folder

JS Getting Started basics (if else and switch Case/node installation)