二、JSON数据格式
时间:2022-07-23
本文章向大家介绍二、JSON数据格式,主要内容包括其使用实例、应用技巧、基本知识点总结和需要注意事项,具有一定的参考价值,需要的朋友可以参考一下。
JSON语法规则
- ”名称/值“对的集合。例如对象、字典 { "name": "好人", "job": [1, 2, 3, 4, 5] }字符串必须使用双引号。
- 值的有序列表。例如数组。 [ 1,2,3 ]
JSON的值可以是字符串、数值、布尔值、null、对象、数组。
JSON可以独立成文件,扩展名为json。
JavaScript中的JSON
- json字符串 数据格式符合JSON格式的要求,类型是字符串 var jsonString = '{"name":"张无忌"}'
- json对象 JSON数据格式在JavaScript中的具体表现 var jsonObject = { name:'张无忌' } var jsonArr = [1,2,3]
JSON对象与JSON字符串转换
- 将json格式字符串转为JSON对象 // json字符串 var jsonString = '{"name":"张无忌"}' var jsonObject = JSON.parse(jsonString) console.log(jsonObject)
- 将json对象转换为JSON字符串 var jsonString = '{"name":"张无忌"}' var jsonObject = JSON.parse(jsonString) var jsonResult = JSON.stringify(jsonObject) console.log(jsonResult)
浏览器兼容问题
引入json2.js文件之后即可正常操作。
// json2.js
// 2017-06-12
// Public Domain.
// NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
// USE YOUR OWN COPY. IT IS EXTREMELY UNWISE TO LOAD CODE FROM SERVERS YOU DO
// NOT CONTROL.
// This file creates a global JSON object containing two methods: stringify
// and parse. This file provides the ES5 JSON capability to ES3 systems.
// If a project might run on IE8 or earlier, then this file should be included.
// This file does nothing on ES5 systems.
// JSON.stringify(value, replacer, space)
// value any JavaScript value, usually an object or array.
// replacer an optional parameter that determines how object
// values are stringified for objects. It can be a
// function or an array of strings.
// space an optional parameter that specifies the indentation
// of nested structures. If it is omitted, the text will
// be packed without extra whitespace. If it is a number,
// it will specify the number of spaces to indent at each
// level. If it is a string (such as "t" or " "),
// it contains the characters used to indent at each level.
// This method produces a JSON text from a JavaScript value.
// When an object value is found, if the object contains a toJSON
// method, its toJSON method will be called and the result will be
// stringified. A toJSON method does not serialize: it returns the
// value represented by the name/value pair that should be serialized,
// or undefined if nothing should be serialized. The toJSON method
// will be passed the key associated with the value, and this will be
// bound to the value.
// For example, this would serialize Dates as ISO strings.
// Date.prototype.toJSON = function (key) {
// function f(n) {
// // Format integers to have at least two digits.
// return (n < 10)
// ? "0" + n
// : n;
// }
// return this.getUTCFullYear() + "-" +
// f(this.getUTCMonth() + 1) + "-" +
// f(this.getUTCDate()) + "T" +
// f(this.getUTCHours()) + ":" +
// f(this.getUTCMinutes()) + ":" +
// f(this.getUTCSeconds()) + "Z";
// };
// You can provide an optional replacer method. It will be passed the
// key and value of each member, with this bound to the containing
// object. The value that is returned from your method will be
// serialized. If your method returns undefined, then the member will
// be excluded from the serialization.
// If the replacer parameter is an array of strings, then it will be
// used to select the members to be serialized. It filters the results
// such that only members with keys listed in the replacer array are
// stringified.
// Values that do not have JSON representations, such as undefined or
// functions, will not be serialized. Such values in objects will be
// dropped; in arrays they will be replaced with null. You can use
// a replacer function to replace those with JSON values.
// JSON.stringify(undefined) returns undefined.
// The optional space parameter produces a stringification of the
// value that is filled with line breaks and indentation to make it
// easier to read.
// If the space parameter is a non-empty string, then that string will
// be used for indentation. If the space parameter is a number, then
// the indentation will be that many spaces.
// Example:
// text = JSON.stringify(["e", {pluribus: "unum"}]);
// // text is '["e",{"pluribus":"unum"}]'
// text = JSON.stringify(["e", {pluribus: "unum"}], null, "t");
// // text is '[nt"e",nt{ntt"pluribus": "unum"nt}n]'
// text = JSON.stringify([new Date()], function (key, value) {
// return this[key] instanceof Date
// ? "Date(" + this[key] + ")"
// : value;
// });
// // text is '["Date(---current time---)"]'
// JSON.parse(text, reviver)
// This method parses a JSON text to produce an object or array.
// It can throw a SyntaxError exception.
// The optional reviver parameter is a function that can filter and
// transform the results. It receives each of the keys and values,
// and its return value is used instead of the original value.
// If it returns what it received, then the structure is not modified.
// If it returns undefined then the member is deleted.
// Example:
// // Parse the text. Values that look like ISO date strings will
// // be converted to Date objects.
// myData = JSON.parse(text, function (key, value) {
// var a;
// if (typeof value === "string") {
// a =
// /^(d{4})-(d{2})-(d{2})T(d{2}):(d{2}):(d{2}(?:.d*)?)Z$/.exec(value);
// if (a) {
// return new Date(Date.UTC(
// +a[1], +a[2] - 1, +a[3], +a[4], +a[5], +a[6]
// ));
// }
// return value;
// }
// });
// myData = JSON.parse(
// "["Date(09/09/2001)"]",
// function (key, value) {
// var d;
// if (
// typeof value === "string"
// && value.slice(0, 5) === "Date("
// && value.slice(-1) === ")"
// ) {
// d = new Date(value.slice(5, -1));
// if (d) {
// return d;
// }
// }
// return value;
// }
// );
// This is a reference implementation. You are free to copy, modify, or
// redistribute.
/*jslint
eval, for, this
*/
/*property
JSON, apply, call, charCodeAt, getUTCDate, getUTCFullYear, getUTCHours,
getUTCMinutes, getUTCMonth, getUTCSeconds, hasOwnProperty, join,
lastIndex, length, parse, prototype, push, replace, slice, stringify,
test, toJSON, toString, valueOf
*/
// Create a JSON object only if one does not already exist. We create the
// methods in a closure to avoid creating global variables.
if (typeof JSON !== "object") {
JSON = {};
}
(function () {
"use strict";
var rx_one = /^[],:{}s]*$/;
var rx_two = /\(?:["\/bfnrt]|u[0-9a-fA-F]{4})/g;
var rx_three = /"[^"\nr]*"|true|false|null|-?d+(?:.d*)?(?:[eE][+-]?d+)?/g;
var rx_four = /(?:^|:|,)(?:s*[)+/g;
var rx_escapable = /[\"u0000-u001fu007f-u009fu00adu0600-u0604u070fu17b4u17b5u200c-u200fu2028-u202fu2060-u206fufeffufff0-uffff]/g;
var rx_dangerous = /[u0000u00adu0600-u0604u070fu17b4u17b5u200c-u200fu2028-u202fu2060-u206fufeffufff0-uffff]/g;
function f(n) {
// Format integers to have at least two digits.
return (n < 10)
? "0" + n
: n;
}
function this_value() {
return this.valueOf();
}
if (typeof Date.prototype.toJSON !== "function") {
Date.prototype.toJSON = function () {
return isFinite(this.valueOf())
? (
this.getUTCFullYear()
+ "-"
+ f(this.getUTCMonth() + 1)
+ "-"
+ f(this.getUTCDate())
+ "T"
+ f(this.getUTCHours())
+ ":"
+ f(this.getUTCMinutes())
+ ":"
+ f(this.getUTCSeconds())
+ "Z"
)
: null;
};
Boolean.prototype.toJSON = this_value;
Number.prototype.toJSON = this_value;
String.prototype.toJSON = this_value;
}
var gap;
var indent;
var meta;
var rep;
function quote(string) {
// If the string contains no control characters, no quote characters, and no
// backslash characters, then we can safely slap some quotes around it.
// Otherwise we must also replace the offending characters with safe escape
// sequences.
rx_escapable.lastIndex = 0;
return rx_escapable.test(string)
? """ + string.replace(rx_escapable, function (a) {
var c = meta[a];
return typeof c === "string"
? c
: "\u" + ("0000" + a.charCodeAt(0).toString(16)).slice(-4);
}) + """
: """ + string + """;
}
function str(key, holder) {
// Produce a string from holder[key].
var i; // The loop counter.
var k; // The member key.
var v; // The member value.
var length;
var mind = gap;
var partial;
var value = holder[key];
// If the value has a toJSON method, call it to obtain a replacement value.
if (
value
&& typeof value === "object"
&& typeof value.toJSON === "function"
) {
value = value.toJSON(key);
}
// If we were called with a replacer function, then call the replacer to
// obtain a replacement value.
if (typeof rep === "function") {
value = rep.call(holder, key, value);
}
// What happens next depends on the value's type.
switch (typeof value) {
case "string":
return quote(value);
case "number":
// JSON numbers must be finite. Encode non-finite numbers as null.
return (isFinite(value))
? String(value)
: "null";
case "boolean":
case "null":
// If the value is a boolean or null, convert it to a string. Note:
// typeof null does not produce "null". The case is included here in
// the remote chance that this gets fixed someday.
return String(value);
// If the type is "object", we might be dealing with an object or an array or
// null.
case "object":
// Due to a specification blunder in ECMAScript, typeof null is "object",
// so watch out for that case.
if (!value) {
return "null";
}
// Make an array to hold the partial results of stringifying this object value.
gap += indent;
partial = [];
// Is the value an array?
if (Object.prototype.toString.apply(value) === "[object Array]") {
// The value is an array. Stringify every element. Use null as a placeholder
// for non-JSON values.
length = value.length;
for (i = 0; i < length; i += 1) {
partial[i] = str(i, value) || "null";
}
// Join all of the elements together, separated with commas, and wrap them in
// brackets.
v = partial.length === 0
? "[]"
: gap
? (
"[n"
+ gap
+ partial.join(",n" + gap)
+ "n"
+ mind
+ "]"
)
: "[" + partial.join(",") + "]";
gap = mind;
return v;
}
// If the replacer is an array, use it to select the members to be stringified.
if (rep && typeof rep === "object") {
length = rep.length;
for (i = 0; i < length; i += 1) {
if (typeof rep[i] === "string") {
k = rep[i];
v = str(k, value);
if (v) {
partial.push(quote(k) + (
(gap)
? ": "
: ":"
) + v);
}
}
}
} else {
// Otherwise, iterate through all of the keys in the object.
for (k in value) {
if (Object.prototype.hasOwnProperty.call(value, k)) {
v = str(k, value);
if (v) {
partial.push(quote(k) + (
(gap)
? ": "
: ":"
) + v);
}
}
}
}
// Join all of the member texts together, separated with commas,
// and wrap them in braces.
v = partial.length === 0
? "{}"
: gap
? "{n" + gap + partial.join(",n" + gap) + "n" + mind + "}"
: "{" + partial.join(",") + "}";
gap = mind;
return v;
}
}
// If the JSON object does not yet have a stringify method, give it one.
if (typeof JSON.stringify !== "function") {
meta = { // table of character substitutions
"b": "\b",
"t": "\t",
"n": "\n",
"f": "\f",
"r": "\r",
""": "\"",
"\": "\\"
};
JSON.stringify = function (value, replacer, space) {
// The stringify method takes a value and an optional replacer, and an optional
// space parameter, and returns a JSON text. The replacer can be a function
// that can replace values, or an array of strings that will select the keys.
// A default replacer method can be provided. Use of the space parameter can
// produce text that is more easily readable.
var i;
gap = "";
indent = "";
// If the space parameter is a number, make an indent string containing that
// many spaces.
if (typeof space === "number") {
for (i = 0; i < space; i += 1) {
indent += " ";
}
// If the space parameter is a string, it will be used as the indent string.
} else if (typeof space === "string") {
indent = space;
}
// If there is a replacer, it must be a function or an array.
// Otherwise, throw an error.
rep = replacer;
if (replacer && typeof replacer !== "function" && (
typeof replacer !== "object"
|| typeof replacer.length !== "number"
)) {
throw new Error("JSON.stringify");
}
// Make a fake root object containing our value under the key of "".
// Return the result of stringifying the value.
return str("", {"": value});
};
}
// If the JSON object does not yet have a parse method, give it one.
if (typeof JSON.parse !== "function") {
JSON.parse = function (text, reviver) {
// The parse method takes a text and an optional reviver function, and returns
// a JavaScript value if the text is a valid JSON text.
var j;
function walk(holder, key) {
// The walk method is used to recursively walk the resulting structure so
// that modifications can be made.
var k;
var v;
var value = holder[key];
if (value && typeof value === "object") {
for (k in value) {
if (Object.prototype.hasOwnProperty.call(value, k)) {
v = walk(value, k);
if (v !== undefined) {
value[k] = v;
} else {
delete value[k];
}
}
}
}
return reviver.call(holder, key, value);
}
// Parsing happens in four stages. In the first stage, we replace certain
// Unicode characters with escape sequences. JavaScript handles many characters
// incorrectly, either silently deleting them, or treating them as line endings.
text = String(text);
rx_dangerous.lastIndex = 0;
if (rx_dangerous.test(text)) {
text = text.replace(rx_dangerous, function (a) {
return (
"\u"
+ ("0000" + a.charCodeAt(0).toString(16)).slice(-4)
);
});
}
// In the second stage, we run the text against regular expressions that look
// for non-JSON patterns. We are especially concerned with "()" and "new"
// because they can cause invocation, and "=" because it can cause mutation.
// But just to be safe, we want to reject all unexpected forms.
// We split the second stage into 4 regexp operations in order to work around
// crippling inefficiencies in IE's and Safari's regexp engines. First we
// replace the JSON backslash pairs with "@" (a non-JSON character). Second, we
// replace all simple value tokens with "]" characters. Third, we delete all
// open brackets that follow a colon or comma or that begin the text. Finally,
// we look to see that the remaining characters are only whitespace or "]" or
// "," or ":" or "{" or "}". If that is so, then the text is safe for eval.
if (
rx_one.test(
text
.replace(rx_two, "@")
.replace(rx_three, "]")
.replace(rx_four, "")
)
) {
// In the third stage we use the eval function to compile the text into a
// JavaScript structure. The "{" operator is subject to a syntactic ambiguity
// in JavaScript: it can begin a block or an object literal. We wrap the text
// in parens to eliminate the ambiguity.
j = eval("(" + text + ")");
// In the optional fourth stage, we recursively walk the new structure, passing
// each name/value pair to a reviver function for possible transformation.
return (typeof reviver === "function")
? walk({"": j}, "")
: j;
}
// If the text is not JSON parseable, then a SyntaxError is thrown.
throw new SyntaxError("JSON.parse");
};
}
}());
Ajax中的JSON
var xhr = createXMLHttpRequest()
var obj = {
name: '1'
}
xhr.open('get', 'server.json?name' + obj.name)
xhr.send(null)
Ajax中的XML
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<button id="btn">按钮</button>
<script src="1.%20createXMLHttpRequest.js"></script>
<script>
var btn = document.getElementById('btn')
btn.addEventListener('click', function () {
var xhr = createXMLHttpRequest()
xhr.open('get', '3. xml数据格式.xml')
xhr.send(null)
xhr.onreadystatechange = function () {
if (xhr.readyState === 4 && xhr.status === 200) {
// 接收数据
console.log(xhr.responseXML)
}
}
})
</script>
</body>
</html>
<?xml version='1.0' encoding='utf-8' ?>
<body>
<name>张无忌</name>
</body>
三级联动案例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<select id="province">
</select>
<select id="cities">
<option value="">---</option>
</select>
<select id="counties">
<option value="">---</option>
</select>
<script>
var xhr = createXMLHttpRequest()
var provinceElement = document.getElementById('province')
var cityElement = document.getElementById('cities')
var countiesElement = document.getElementById('counties')
var datas;
xhr.onreadystatechange = function () {
if (xhr.readyState === 4 && xhr.status === 200) {
var response = xhr.responseText
datas = JSON.parse(response)
console.log(datas);
for (var i = 0; i < datas.length; i++) {
var data = datas[i]
var opt = document.createElement('option')
opt.setAttribute('value', data.province)
opt.textContent = data.province
provinceElement.appendChild(opt)
}
}
}
xhr.open('get', 'data/server1.json')
xhr.send(null)
// 为省份下拉列表绑定事件change
provinceElement.addEventListener('change', function () {
var cityOpts = cityElement.options
for (var k = 1; k < cityOpts.length; k++) {
cityElement.removeChild(cityOpts[k])
k--
}
var opts = provinceElement.options
var index = provinceElement.selectedIndex
var opt = opts.item(index)
var provinceName = opt.getAttribute('value')
// 2. 根据省份信息获取城市信息
for (var i = 0; i < datas.length; i++) {
var data = datas[i]
var province = data.province
if (provinceName === province) {
var cities = data.cities
for (var j = 0; j < cities.length; j++) {
var city = cities[j].city
var opt = document.createElement('option')
opt.setAttribute('value', city)
opt.textContent = city
cityElement.appendChild(opt)
}
}
}
})
function createXMLHttpRequest() {
var httpRequest;
if (window.XMLHttpRequest) {
// 适用于非IE浏览器
httpRequest = new XMLHttpRequest();
} else if (window.ActiveXObject) {
// 适用于IE浏览器
try {
// IE 7+
httpRequest = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
// IE 6-
httpRequest = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e) { }
}
}
return httpRequest;
}
</script>
</body>
</html>
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