How to create arrays (two ways)

1: Create arrays using literals

How to determine whether something is an array

Ways to add or remove elements in an array

Sorting the array

Array indexing methods

Use indexOf, for example: arr.indexOf(yuan);// It searches from front to back
Use lastIndexOf, for example: arr1.lastIndexOf(yuan);// It searches from back to front.
Note that if the array does not contain that content, it will return -1.

Characters returned from a string

Using charAt, you can return the character at the corresponding position in the string.
Using charCodeAt, it returns the ASCII code of the corresponding character in the string.
str[index], returns the character as a string. It is used in HTML5, with compatibility issues.

Convert an array to a string (string type)

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