1. 背景：
平时不知道用js写什么练手，这里就写了一个类似百度翻译的小demo。大家可以平时没事儿了看看书，写写像这种类型的小demo,调用以下公开的api即可。对于学生党，能进入学校实验室做项目更好。进不去的，平时写写小demo练练也不差。(我为什么没在实验室)
2. demo前准备工作：
页面布局
了解百度翻译API，所需配置参数
准备 MD5.js 加密算法函数（百度自己搜）
写js代码
3. 步骤：
1. 页面布局：
布局就不说了，直接贴图上代码：
可进行语言切换
html代码：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<link rel="stylesheet" type="text/css" href="css/style.css">
</head>
<body>
<div id="main">
<div class="left">
<div class="title">
要翻译为：
<span class="lang">英文</span>
<ul class="ul1">
<li data-lang="en">英语</li>
<li data-lang="zh">中文</li>
<li data-lang="jp">日语</li>
<li data-lang="kor">韩语</li>
<li data-lang="fra">法语</li>
<li data-lang="ru">俄语</li>
<li data-lang="de">德语</li>
</ul>
</div>
<textarea class="text" placeholder="要翻译的单词/句子" value=""></textarea>
</div>
<div class="right">
<div class="title">翻译结果：</div>
<div class="cont"></div>
</div>
<div class="bottom">
<button class="reset">清除</button>
<button class="trans">翻译</button>
</div>
</div>
<script src="js/MD5.js"></script>
<script src="js/script.js"></script>
</body>
</html>
css代码：
*{
margin: 0;
padding: 0;
font-family: "微软雅黑";
}
html,body {
height: 100%;
}
li {
list-style: none;
}
body {
overflow: hidden;
}
#main {
width: 1000px;
height: 80%;
margin: 5% auto;
}
#main .left {
float: left;
width: 350px;
height:330px;
margin: 50px 0 0 50px;
background-color: #fff;
border: 1px solid #000;
box-sizing: border-box;
color: #fff;
border-top-left-radius: 15px;
border-top-right-radius: 15px;
}
#main .right {
float: right;
width: 350px;
height: 330px;
margin: 50px 50px 0 0;
background-color: #fff;
box-sizing: border-box;
border: 1px solid #000;
border-top-left-radius: 15px;
border-top-right-radius: 15px;
}
#main .title {
width: 100%;
height: 40px;
background-color: #333;
line-height: 40px;
text-indent: 20px;
position: relative;
color: #fff;
border-top-left-radius: 15px;
border-top-right-radius: 15px;
}
#main .lang {
height: 40px;
line-height: 40px;
text-indent: 20px;
letter-spacing: 2px;
text-decoration: underline;
color: #58a;
cursor: pointer;
}
#main .lang:hover {
text-decoration: none;
color: #eee;
}
#main .text {
width: 100%;
height: 288px;
padding: 20px;
box-sizing: border-box;
resize: none;
outline: none;
border: none;
}
#main .right .cont {
width: 100%;
height: 295px;
padding: 20px;
box-sizing: border-box;
}
#main .bottom {
float: left;
width: 100%;
height: 40px;
margin-top: 60px;
}
#main .bottom button {
float: right;
width: 65px;
height: 35px;
line-height: 35px;
letter-spacing: 2px;
border: none;
margin-right: 50px;
border-radius: 3px;
outline: none;
cursor: pointer;
color: #eee;
background-color: #333;
}
#main ul {
width: 100%;
padding: 20px 15px 0 20px;
box-sizing: border-box;
position: absolute;
background: blue;
background-color: #fff;
border-bottom: 1px solid #333;
display: none;
}
#main ul li {
float:left;
text-indent: 0;
text-align: center;
padding: 0 10px;
margin: 0 10px;
margin-bottom: 20px;
border: 1px solid #000;
border-radius: 5px;
box-sizing: border-box;
color: #333;
cursor: pointer;
}
#main ul li:hover {
background-color: #333;
color: #fff;
}
2，了解百度翻译API
这只只对所配置的参数做一介绍，官方API也有做解释：
进入百度翻译，左下角如图：
点击百度翻译开放平台：
q是你要翻译的字符串
from是你在输入时的语言
to是你要翻译成什么语言
appid是你申请的百度翻译测试账号（注册后秒发）
salt是一个随机数，这里用事件表示
sign是对拼接的字符串的MD5加密，至于拼接的字符串其实就是： 待加密字符串 =
appid+q+salt+秘钥（申请账号时密码也会给你） 最后把 待价密 的字符串传入MD5函数，返回sign.
完整流程如图：
3.准备MD5加密函数（可以百度自己搜，这里直接附代码）
MD5加密字符串：
var MD5 = function (string) {
function RotateLeft(lValue, iShiftBits) {
return (lValue<<iShiftBits) | (lValue>>>(32-iShiftBits));
}
function AddUnsigned(lX,lY) {
var lX4,lY4,lX8,lY8,lResult;
lX8 = (lX & 0x80000000);
lY8 = (lY & 0x80000000);
lX4 = (lX & 0x40000000);
lY4 = (lY & 0x40000000);
lResult = (lX & 0x3FFFFFFF)+(lY & 0x3FFFFFFF);
if (lX4 & lY4) {
return (lResult ^ 0x80000000 ^ lX8 ^ lY8);
}
if (lX4 | lY4) {
if (lResult & 0x40000000) {
return (lResult ^ 0xC0000000 ^ lX8 ^ lY8);
} else {
return (lResult ^ 0x40000000 ^ lX8 ^ lY8);
}
} else {
return (lResult ^ lX8 ^ lY8);
}
}
function F(x,y,z) { return (x & y) | ((~x) & z); }
function G(x,y,z) { return (x & z) | (y & (~z)); }
function H(x,y,z) { return (x ^ y ^ z); }
function I(x,y,z) { return (y ^ (x | (~z))); }
function FF(a,b,c,d,x,s,ac) {
a = AddUnsigned(a, AddUnsigned(AddUnsigned(F(b, c, d), x), ac));
return AddUnsigned(RotateLeft(a, s), b);
};
function GG(a,b,c,d,x,s,ac) {
a = AddUnsigned(a, AddUnsigned(AddUnsigned(G(b, c, d), x), ac));
return AddUnsigned(RotateLeft(a, s), b);
};
function HH(a,b,c,d,x,s,ac) {
a = AddUnsigned(a, AddUnsigned(AddUnsigned(H(b, c, d), x), ac));
return AddUnsigned(RotateLeft(a, s), b);
};
function II(a,b,c,d,x,s,ac) {
a = AddUnsigned(a, AddUnsigned(AddUnsigned(I(b, c, d), x), ac));
return AddUnsigned(RotateLeft(a, s), b);
};
function ConvertToWordArray(string) {
var lWordCount;
var lMessageLength = string.length;
var lNumberOfWords_temp1=lMessageLength + 8;
var lNumberOfWords_temp2=(lNumberOfWords_temp1-(lNumberOfWords_temp1 % 64))/64;
var lNumberOfWords = (lNumberOfWords_temp2+1)*16;
var lWordArray=Array(lNumberOfWords-1);
var lBytePosition = 0;
var lByteCount = 0;
while ( lByteCount < lMessageLength ) {
lWordCount = (lByteCount-(lByteCount % 4))/4;
lBytePosition = (lByteCount % 4)*8;
lWordArray[lWordCount] = (lWordArray[lWordCount] | (string.charCodeAt(lByteCount)<<lBytePosition));
lByteCount++;
}
lWordCount = (lByteCount-(lByteCount % 4))/4;
lBytePosition = (lByteCount % 4)*8;
lWordArray[lWordCount] = lWordArray[lWordCount] | (0x80<<lBytePosition);
lWordArray[lNumberOfWords-2] = lMessageLength<<3;
lWordArray[lNumberOfWords-1] = lMessageLength>>>29;
return lWordArray;
};
function WordToHex(lValue) {
var WordToHexValue="",WordToHexValue_temp="",lByte,lCount;
for (lCount = 0;lCount<=3;lCount++) {
lByte = (lValue>>>(lCount*8)) & 255;
WordToHexValue_temp = "0" + lByte.toString(16);
WordToHexValue = WordToHexValue + WordToHexValue_temp.substr(WordToHexValue_temp.length-2,2);
}
return WordToHexValue;
};
function Utf8Encode(string) {
string = string.replace(/\r\n/g,"\n");
var utftext = "";
for (var n = 0; n < string.length; n++) {
var c = string.charCodeAt(n);
if (c < 128) {
utftext += String.fromCharCode(c);
}
else if((c > 127) && (c < 2048)) {
utftext += String.fromCharCode((c >> 6) | 192);
utftext += String.fromCharCode((c & 63) | 128);
}
else {
utftext += String.fromCharCode((c >> 12) | 224);
utftext += String.fromCharCode(((c >> 6) & 63) | 128);
utftext += String.fromCharCode((c & 63) | 128);
}
}
return utftext;
};
var x=Array();
var k,AA,BB,CC,DD,a,b,c,d;
var S11=7, S12=12, S13=17, S14=22;
var S21=5, S22=9 , S23=14, S24=20;
var S31=4, S32=11, S33=16, S34=23;
var S41=6, S42=10, S43=15, S44=21;
string = Utf8Encode(string);
x = ConvertToWordArray(string);
a = 0x67452301; b = 0xEFCDAB89; c = 0x98BADCFE; d = 0x10325476;
for (k=0;k<x.length;k+=16) {
AA=a; BB=b; CC=c; DD=d;
a=FF(a,b,c,d,x[k+0], S11,0xD76AA478);
d=FF(d,a,b,c,x[k+1], S12,0xE8C7B756);
c=FF(c,d,a,b,x[k+2], S13,0x242070DB);
b=FF(b,c,d,a,x[k+3], S14,0xC1BDCEEE);
a=FF(a,b,c,d,x[k+4], S11,0xF57C0FAF);
d=FF(d,a,b,c,x[k+5], S12,0x4787C62A);
c=FF(c,d,a,b,x[k+6], S13,0xA8304613);
b=FF(b,c,d,a,x[k+7], S14,0xFD469501);
a=FF(a,b,c,d,x[k+8], S11,0x698098D8);
d=FF(d,a,b,c,x[k+9], S12,0x8B44F7AF);
c=FF(c,d,a,b,x[k+10],S13,0xFFFF5BB1);
b=FF(b,c,d,a,x[k+11],S14,0x895CD7BE);
a=FF(a,b,c,d,x[k+12],S11,0x6B901122);
d=FF(d,a,b,c,x[k+13],S12,0xFD987193);
c=FF(c,d,a,b,x[k+14],S13,0xA679438E);
b=FF(b,c,d,a,x[k+15],S14,0x49B40821);
a=GG(a,b,c,d,x[k+1], S21,0xF61E2562);
d=GG(d,a,b,c,x[k+6], S22,0xC040B340);
c=GG(c,d,a,b,x[k+11],S23,0x265E5A51);
b=GG(b,c,d,a,x[k+0], S24,0xE9B6C7AA);
a=GG(a,b,c,d,x[k+5], S21,0xD62F105D);
d=GG(d,a,b,c,x[k+10],S22,0x2441453);
c=GG(c,d,a,b,x[k+15],S23,0xD8A1E681);
b=GG(b,c,d,a,x[k+4], S24,0xE7D3FBC8);
a=GG(a,b,c,d,x[k+9], S21,0x21E1CDE6);
d=GG(d,a,b,c,x[k+14],S22,0xC33707D6);
c=GG(c,d,a,b,x[k+3], S23,0xF4D50D87);
b=GG(b,c,d,a,x[k+8], S24,0x455A14ED);
a=GG(a,b,c,d,x[k+13],S21,0xA9E3E905);
d=GG(d,a,b,c,x[k+2], S22,0xFCEFA3F8);
c=GG(c,d,a,b,x[k+7], S23,0x676F02D9);
b=GG(b,c,d,a,x[k+12],S24,0x8D2A4C8A);
a=HH(a,b,c,d,x[k+5], S31,0xFFFA3942);
d=HH(d,a,b,c,x[k+8], S32,0x8771F681);
c=HH(c,d,a,b,x[k+11],S33,0x6D9D6122);
b=HH(b,c,d,a,x[k+14],S34,0xFDE5380C);
a=HH(a,b,c,d,x[k+1], S31,0xA4BEEA44);
d=HH(d,a,b,c,x[k+4], S32,0x4BDECFA9);
c=HH(c,d,a,b,x[k+7], S33,0xF6BB4B60);
b=HH(b,c,d,a,x[k+10],S34,0xBEBFBC70);
a=HH(a,b,c,d,x[k+13],S31,0x289B7EC6);
d=HH(d,a,b,c,x[k+0], S32,0xEAA127FA);
c=HH(c,d,a,b,x[k+3], S33,0xD4EF3085);
b=HH(b,c,d,a,x[k+6], S34,0x4881D05);
a=HH(a,b,c,d,x[k+9], S31,0xD9D4D039);
d=HH(d,a,b,c,x[k+12],S32,0xE6DB99E5);
c=HH(c,d,a,b,x[k+15],S33,0x1FA27CF8);
b=HH(b,c,d,a,x[k+2], S34,0xC4AC5665);
a=II(a,b,c,d,x[k+0], S41,0xF4292244);
d=II(d,a,b,c,x[k+7], S42,0x432AFF97);
c=II(c,d,a,b,x[k+14],S43,0xAB9423A7);
b=II(b,c,d,a,x[k+5], S44,0xFC93A039);
a=II(a,b,c,d,x[k+12],S41,0x655B59C3);
d=II(d,a,b,c,x[k+3], S42,0x8F0CCC92);
c=II(c,d,a,b,x[k+10],S43,0xFFEFF47D);
b=II(b,c,d,a,x[k+1], S44,0x85845DD1);
a=II(a,b,c,d,x[k+8], S41,0x6FA87E4F);
d=II(d,a,b,c,x[k+15],S42,0xFE2CE6E0);
c=II(c,d,a,b,x[k+6], S43,0xA3014314);
b=II(b,c,d,a,x[k+13],S44,0x4E0811A1);
a=II(a,b,c,d,x[k+4], S41,0xF7537E82);
d=II(d,a,b,c,x[k+11],S42,0xBD3AF235);
c=II(c,d,a,b,x[k+2], S43,0x2AD7D2BB);
b=II(b,c,d,a,x[k+9], S44,0xEB86D391);
a=AddUnsigned(a,AA);
b=AddUnsigned(b,BB);
c=AddUnsigned(c,CC);
d=AddUnsigned(d,DD);
}
var temp = WordToHex(a)+WordToHex(b)+WordToHex(c)+WordToHex(d);
return temp.toLowerCase();
}
加密：
发送请求时别忘了在参数最后面加上一个callback参数用来接收返回值
callback函数：
function fn(str) {
var result = document.querySelector(".right .cont");
result.innerHTML = str.trans_result[0].dst;
}
4.写js
这里简单的逻辑就不说了，说说这里的接口请求的实现和实现实时翻译的逻辑（每输入一两个字就会主动给你翻译）。首先这个列子的核心就是jsonp的跨域请求原理很简单，就是每次请求都给他创建一个<script>标签插入body, 每次给标签的src传入不同的参数，待服务器给你返回数据，最终拿到数据渲染到页面。这里要提醒的是要给请求的参数最后面加上一个回调函数，返回过来的数据客户端可以从回调函数中拿取。其次就是实时翻译，原理就是在敲键盘时每次按键抬起时隔一定的时间去请求，那就是键盘事件加上setInterval();每隔500ms去请求。
整个过程的代码如下：
(function() {
var title = document.querySelector(".left .title .lang"),
ul = document.querySelector(".ul1"),
lis = document.querySelectorAll(".ul1 li"),
text = document.querySelector(".left .text"),
result = document.querySelector(".right .cont"),
reset = document.querySelector(".bottom .reset"),
trans = document.querySelector(".bottom .trans"),
key = true,
length = lis.length,
lang = "en",
timer = null;
function langShow() {
if (key == true) {
ul.style.display = "block";
key = false;
} else {
ul.style.display = "none";
key = true;
}
}
function changeLang() {
lang = this.getAttribute('data-lang');
title.innerHTML = this.innerHTML;
this.parentNode.style.display = "none";
key = true;
}
function createScript(src) {
var script = document.createElement('script');
script.id = "script1"
script.src = src;
document.body.appendChild(script);
}
function translate() {
var value = 'http://api.fanyi.baidu.com/api/trans/vip/translate?';
var date = Date.now();
var str = '20170605000052254'+text.value+date+'63r1c42X7_buc4OrXm1g';
var md5 = MD5(str);
var data = 'q=' + text.value + '&from=auto&to=' + lang + '&appid=20170605000052254' + '&salt=' + date + '&sign=' + md5 + "&callback=fn";
var src = value + data;
createScript(src);
}
function init() {
title.onclick = langShow;
for (var i = 0; i < length; i++) {
lis[i].onclick = changeLang;
}
reset.onclick = function() {
text.value = "";
}
trans.onclick = function() {
if (text.value == "") {
return;
}
var script = document.querySelector('#script1');
if (script) {
script.parentNode.removeChild(script);
translate();
} else {
translate();
}
}
text.onkeydown = function() {
clearTimeout(timer);
timer = setInterval(function() {
if (text.value == "") {
return;
}
var script = document.querySelector('#script1');
if (script) {
script.parentNode.removeChild(script);
translate();
} else {
translate();
}
}, 500);
clearTimeout(timer);
}
}
init();
})();
function fn(str) {
var result = document.querySelector(".right .cont");
result.innerHTML = str.trans_result[0].dst;
}
以上就是实现翻译的过程，效果图：
中 - 英
中 - 韩
这样一个小小的翻译小Demo就完成了，主要还是练习原生js，理解跨域请求的原理，其实跨域请求的方法很多，比如<img>标签的src，<iframe>等等。这些方法大家都得去一一了解。
本文分享到此结束，笔者技术有限，理解有误的地方还请大家多提，大家可以共同学习。
html5
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