JavaScript knowledge points

One, String type

1. Use IndexOf () to position the first occurrence of a specified character in a string.

var str= "Hello world!"
document.write (Str.indexof ("Hello") + "<br/>") 0

document.write (Str.indexof ("World") + "<br/>")-1

document.write (Str.indexof ("World")) 6

2. Use Match () to find a specific character in the string and, if found, return the character.

var str= "Hello world!"
document.write (Str.match ("World") + "<br/>") World
document.write (Str.match ("World") + "<br/>") null
document.write (Str.match ("worlld") + "<br/>") null
document.write (Str.match ("world!")) world!

3. Use the Replace () method to replace characters with some characters in a string.

var str= "Visit microsoft!"
document.write (Str.replace (/microsoft/, "W3school")) Visit w3school!

II, Json.parse () and Json.stringify ()

1.parse is used to parse a JSON object from a string, such as

var str = ' {' name ': ' Huangxiaojian ', ' age ': ' 23 '} '

Json.parse (str)

Results:

Object

　　Age: "All"

name: "Huangxiaojian"

__proto__: Object

Note: Single quotes are written in {}, each property name must be in double quotation marks, or an exception will be thrown.

2.stringify () is used to parse out a string from an object, such as

var a = {A:1,b:2}

Json.stringify (a)

Results:

"{" A ": 1," B ": 2}"

JavaScript knowledge points