JavaScript基础16-day18(已完结!)【轮播图、类的操作、二级菜单、JSON】
学习地址：
- 谷粒学院——尚硅谷
- 哔哩哔哩网站——尚硅谷最新版JavaScript基础全套教程完整版(140集实战教学,JS从入门到精通)
JavaScript基础、高级学习笔记汇总表【尚硅谷最新版JavaScript基础全套教程完整版(140集实战教学,JS从入门到精通)】
目 录
P136 136.尚硅谷_JS基础_完成轮播图 26:21
P137 137.尚硅谷_JS基础_类的操作 30:02
1、addClass(obj, cn)：向一个元素中添加指定的class属性值
2、hasClass(obj, cn)：判断一个元素中是否含有指定的class属性值
3、removeClass(obj, cn)：删除一个元素中的指定的class属性
4、toggleClass(obj, cn)：切换一个类
P138 138.尚硅谷_JS基础_二级菜单-完成基本功能 28:54
js/tools.js
P139 139.尚硅谷_JS基础_二级菜单-过渡效果 16:14
P140 140.尚硅谷_JS基础_JSON 37:14
JSON：JavaScript Object Notation JS对象表示法
W3School离线手册——JSON
将JSON字符串转换为JS中的对象
JSON --> JS对象：JSON.parse()
JS对象 ---> JSON：JSON.stringify()
兼容IE
兼容IE7及以下的JSON操作：引入外部的js文件
eval()：执行一段字符串形式的JS代码，并将执行结果返回
JavaScript高级课程：https://www.bilibili.com/video/BV14s411E7qf
P136 136.尚硅谷_JS基础_完成轮播图 26:21
P137 137.尚硅谷_JS基础_类的操作 30:02
1、addClass(obj, cn)：向一个元素中添加指定的class属性值
2、hasClass(obj, cn)：判断一个元素中是否含有指定的class属性值
3、removeClass(obj, cn)：删除一个元素中的指定的class属性
4、toggleClass(obj, cn)：切换一个类
P138 138.尚硅谷_JS基础_二级菜单-完成基本功能 28:54
css/sdmenu.css
/* sdmenu */
@charset "utf-8";
div.sdmenu {
width: 150px;
margin: 0 auto;
font-family: Arial, sans-serif;
font-size: 12px;
padding-bottom: 10px;
background: url(bottom.gif) no-repeat right bottom;
color: #fff;
}
div.sdmenu div {
background: url(title.gif) repeat-x;
overflow: hidden;
}
div.sdmenu div:first-child {
background: url(toptitle.gif) no-repeat;
}
div.sdmenu div.collapsed {
height: 25px;
}
div.sdmenu div span {
display: block;
height: 15px;
line-height: 15px;
overflow: hidden;
padding: 5px 25px;
font-weight: bold;
color: white;
background: url(expanded.gif) no-repeat 10px center;
cursor: pointer;
border-bottom: 1px solid #ddd;
}
div.sdmenu div.collapsed span {
background-image: url(collapsed.gif);
}
div.sdmenu div a {
padding: 5px 10px;
background: #eee;
display: block;
border-bottom: 1px solid #ddd;
color: #066;
}
div.sdmenu div a.current {
background: #ccc;
}
div.sdmenu div a:hover {
background: #066 url(linkarrow.gif) no-repeat right center;
color: #fff;
text-decoration: none;
}js/tools.js
/*尝试创建一个可以执行简单动画的函数
* 参数：
* obj:要执行动画的对象
* attr:要执行动画的样式，比如：left top width height
* target:执行动画的目标位置
* speed:移动的速度(正数向右移动，负数向左移动)
* callback:回调函数，这个函数将会在动画执行完毕以后执行
*/
function move(obj, attr, target, speed, callback) {
//关闭上一个定时器
clearInterval(obj.timer);
//获取元素目前的位置
var current = parseInt(getStyle(obj, attr));
//判断速度的正负值
//如果从0 向 800移动，则speed为正
//如果从800向0移动，则speed为负
if (current > target) {
//此时速度应为负值
speed = -speed;
}
//开启一个定时器，用来执行动画效果
//向执行动画的对象中添加一个timer属性，用来保存它自己的定时器的标识
obj.timer = setInterval(function() {
//获取box1的原来的left值
var oldValue = parseInt(getStyle(obj, attr));
//在旧值的基础上增加
var newValue = oldValue + speed;
//判断newValue是否大于800
//从800 向 0移动
//向左移动时，需要判断newValue是否小于target
//向右移动时，需要判断newValue是否大于target
if ((speed < 0 && newValue < target) || (speed > 0 && newValue > target)) {
newValue = target;
}
//将新值设置给box1
obj.style[attr] = newValue + "px";
//当元素移动到0px时，使其停止执行动画
if (newValue == target) {
//达到目标，关闭定时器
clearInterval(obj.timer);
//动画执行完毕，调用回调函数
callback && callback();
}
}, 30);
}
/*
* 定义一个函数，用来获取指定元素的当前的样式
* 参数：
* obj 要获取样式的元素
* name 要获取的样式名
*/
function getStyle(obj, name) {
if (window.getComputedStyle) {
//正常浏览器的方式，具有getComputedStyle()方法
return getComputedStyle(obj, null)[name];
} else {
//IE8的方式，没有getComputedStyle()方法
return obj.currentStyle[name];
}
}
/*1、定义一个函数，用来向一个元素中添加指定的class属性值
* 参数:
* obj 要添加class属性的元素
* cn 要添加的class值
*
*/
function addClass(obj, cn) {
//检查obj中是否含有cn
if (!hasClass(obj, cn)) {
obj.className += " " + cn;
}
}
/*
* 2、判断一个元素中是否含有指定的class属性值
* 如果有该class，则返回true，没有则返回false
*
*/
function hasClass(obj, cn) {
//判断obj中有没有cn class
//创建一个正则表达式
//var reg = /\bb2\b/;
var reg = new RegExp("\\b" + cn + "\\b");
return reg.test(obj.className);
}
/*
* 3、删除一个元素中的指定的class属性
*/
function removeClass(obj, cn) {
//创建一个正则表达式
var reg = new RegExp("\\b" + cn + "\\b");
//删除class
obj.className = obj.className.replace(reg, "");
}
/*
* 4、toggleClass可以用来切换一个类
* 如果元素中具有该类，则删除
* 如果元素中没有该类，则添加
*/
function toggleClass(obj, cn) {
//判断obj中是否含有cn
if (hasClass(obj, cn)) {
//有，则删除
removeClass(obj, cn);
} else {
//没有，则添加
addClass(obj, cn);
}
}P139 139.尚硅谷_JS基础_二级菜单-过渡效果 16:14
项目文件：JavaScript基础、高级学习笔记汇总表【尚硅谷最新版JavaScript基础全套教程完整版(140集实战教学,JS从入门到精通)】
二级菜单
P140 140.尚硅谷_JS基础_JSON 37:14
JSON：JavaScript Object Notation JS对象表示法
JSON = "JavaScript Object Notation"，称为JS对象标识，是为了给其他语言识别的一种JS包装对象的手段。
- JS中的对象只有JS自己认识，其他的语言都不认识。
- JSON就是一个特殊格式的字符串，这个字符串可以被任意的语言所识别，并且可以转换为任意语言中的对象，JSON在开发中主要用来数据的交互。
- JSON：JavaScript Object Notation JS对象表示法；JSON和JS对象的格式一样，只不过JSON字符串中的属性名必须加双引号，其他的和JS语法一致。
- JSON分类：1.对象 {}；2.数组 []。
- JSON中允许的值：
- 字符串
- 数值
- 布尔值
- null
- 对象
- 数组
W3School离线手册——JSON
将JSON字符串转换为JS中的对象
在JS中，为我们提供了一个工具类，就叫JSON。这个对象可以帮助我们将一个JSON字符串转换为JS中的对象，也可以将一个JS对象转换为JSON。
JSON --> JS对象：JSON.parse()
json --> js对象：JSON.parse()
可以将一个JSON字符串转换为js对象。它需要一个JSON字符串作为参数，会将该字符串转换为JS对象并返回。
JS对象 ---> JSON：JSON.stringify()
JS对象 ---> JSON：JSON.stringify()
可以将一个JS对象转换为JSON字符串，需要一个js对象作为参数，会返回一个JSON字符串。
兼容IE
JSON这个对象在IE7及以下的浏览器中不支持，所以在这些浏览器中调用时会报错。
兼容IE7及以下的JSON操作：引入外部的js文件（json2.js）
如果需要兼容IE7及以下的JSON操作，则可以通过引入一个外部的js文件来处理。
// json2.js
// 2016-05-01
// Public Domain.
// NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
// See http://www.JSON.org/js.html
// This code should be minified before deployment.
// See http://javascript.crockford.com/jsmin.html
// 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 is 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 '[\n\t"e",\n\t{\n\t\t"pluribus": "unum"\n\t}\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 = /"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g;
var rx_four = /(?:^|:|,)(?:\s*\[)+/g;
var rx_escapable =
/[\\\"\u0000-\u001f\u007f-\u009f\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g;
var rx_dangerous =
/[\u0000\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\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");
};
}
}());eval()：执行一段字符串形式的JS代码，并将执行结果返回
eval()
- 这个函数可以用来执行一段字符串形式的JS代码，并将执行结果返回。
- 如果使用eval()执行的字符串中含有{}，它会将{}当成是代码块，如果不希望将其当成代码块解析，则需要在字符串前后各加一个()。
- eval()这个函数的功能很强大，可以直接执行一个字符串中的js代码，但是在开发中尽量不要使用，首先它的执行性能比较差，然后它还具有安全隐患。
JavaScript高级课程：https://www.bilibili.com/video/BV14s411E7qf
感谢李老师。JavaScript专栏（笔记）：https://blog.csdn.net/weixin_44949135/category_10123119.html