Getting started with JS

js

Basic use

1. Introduce external js files (no need to write js code inside)
2. Add in tags

<a href = "Javascript:alert('标签内的')">百度</a>

3. Event based

<p onclick = "alert('基于事件的')">基于事件的</p>

4. Write in the script notes

Three commonly used output methods in JS

1. Console output console.log
2. Alert()
3. Output text content document.write() / window.document.write()

variable

In fact, it is a container
js weakly typed language. What type of value is stored in the variable, then what type is the variable.
If a variable is declared without a value, his system will give him a default value of undefined

Variable naming

1. Variable naming is composed of numbers, letters, underscores, and $, but cannot start with a number
2. Variables are case sensitive. Name and name are not a variable
3. Variable naming, try to be meaningful, you can use English words
4. Hump ​​nomenclature
   Small hump fristName
   Big hump FristName

Comment
Single-line comment
Multi-line comment (be careful not to nest multi-line comments)