js--basic Knowledge (III.)

1. Select

(1) Its selection event is onchange

(2) His option index can be obtained through value, which is a little easier than the Tab tab.

2. Common methods of arrays

(1) Adding elements

Push (): You can add one or more elements to the end of an array and return the length of the new array.

Unshift (): You can add one or more elements to the front of an array and return the length of the new array.

(2) Deleting an array element

Pop (): Deletes the last element value of the array and returns the element value

Shift (): Deletes the value of the first element of the array and returns the element value

(3) Contact (): Connect two or more arrays

Split (): String conversions to arrays

Syntax: array name. split (specify symbol); Specify the symbol: specific case analysis

Example: Var txt= "AA,A,BB,BBB";     Console.log (Txt.split (",")); Print array results: ["AA", "a", "BB", "BBB"]

Join (): Converts each element of an array to a string by specifying a symbol

Syntax: array name. Join (specify symbol); Specify symbol: +-*/space and so on.

Example: Var arr=[1,2,3];  Console.log (Arr.join ("-")); Print string Result: "The"

js--basic Knowledge (III.)