前端学习之（htmldom）(JSON)

找寻方法

document.getelementbyid(id)

document.getelementsbytagname(name)var x = document.getelementsbytagname("p");

document.getelementbyid("demo").innerhtml =?

'the first paragraph (index 0) is: ' +x[2].innerhtml;

document.getelementsbyclassname(name)

var mynodelist = document.queryselectorall("p");? //找寻所有子节点

处理方法

document.write();

document.getelementbyid(id).innerhtml="hello";

document.getelementbyid("myimage").src ="landscape.jpg";? //change attribute

document.getelementbyid("p2").style.color ="blue"; //change css

click on this text!

对节点的定义

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parentnode childnodes[nodenumber] firstchild lastchild nextsibling previoussibling

节点属性

document.getelementbyid("id01").nodename

document.getelementbyid("id01").nodetype

document.getelementsbytagname("p").length

element_node1w3schools

attribute_node2?class = "heading" (deprecated)

text_node3w3schools

comment_node8

document_node9the html document itself (the parent of

document_type_node10

添加节点

json

javascript object notation(for stroage and exchange data)? json就是一个text，也可以理解为string

json uses javascript syntax, but the json format is text only.

text can be read and used as a data format by any programming language.

成对出现，“”括起，{}括起object []array

与xml区别：?xml has to be parsed with an xml parser. json can be parsed by a standard javascript function. (更快read write，short)

可以在object中套用object(myobj.cars["car2"]? //? ?myobj.cars.car2)如果cars是array 用myobj.cars[2]

myobj = {"name":"john","age":30, "car":null };

x = myobj.name;x = myobj["name"];

for (xin myobj) {

??? document.getelementbyid("demo").innerhtml+= x; //输出 name,age car? ? document.getelementbyid("demo").innerhtml+= myobj[x];? //输出 john 30 null}?

json.parse() to convert text into a javascript object:

var arr = ["john", "peter","sally", "jane" ];

var myjson = json.stringify(arr);? //将js转化为json

request json from the server by using an ajax request //利用xmlhttprequest