[心得] 整數轉16進位
note:已經有更快的方法 請看344
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不曉得這邊可不可以貼這種javascript的心得@@a
以前寫16進位轉換的時候
寫出一個雖然很笨但是很直覺好用的方法
用字串索引數字外加用charAt暴力分割字串
最近又拿出來用
突然在想有沒有更快的處理方法
於是做以下測試
測試時使用ie6, opera 8, mozilla firefox 1.0.2
結論:用字串+charAt暴力搜尋最好
方法1,2基本上時間相差沒有很多,ie1跑的比2快
mozilla反之,可是都是0.05秒以內的差距
再說1的程式碼比較短...
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編號 時間 測試項目
1 1953 用字串+charAt暴力切割
2 1969 改用字串表
3 2453 用fromCharCode加上小判斷
4 2360 用暴力字碼表+fromCharCode
5 2016 把1的位元運算改用mod 結論是速度下降
6 2594 把2的字串表改用charAt轉字元表 還是速度下降
7 2469 把3改寫用if else 有比3快可是還是不夠
8 3844 把4的fromCharCode改在建立陣列做
9 4500 把6的charAt(0)改在建立陣列時候做
10 2000 把1的charAt改由subString做 發現會稍慢
---
<script>
function dec2hex(num){
var str16 = "0123456789ABCDEF";
var str = new Array;
for(var i = 0; num > 0; i++){
var tmpNum = num & 0x0F;
str[i] = str16.charAt(tmpNum);
num >>= 4;
}
return str.reverse().join("");
}
function dec2hex2(num){
var str16 = new Array("0","1","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F");
var str = new Array;
for(var i = 0; num > 0; i++){
var tmpNum = num & 0x0F;
str[i] = str16[tmpNum];
num >>= 4;
}
return str.join("");
}
function dec2hex3(num){
var str16 = new Array("0","1","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F");
var str = new Array;
for(var i = 0; num > 0; i++){
var tmpNum = num & 0x0F;
str[i] = String.fromCharCode((tmpNum>9)?(tmpNum+0x30):(tmpNum+0x37));
num >>= 4;
}
return str.reverse().join("");
}
function dec2hex4(num){
var str16 = new Array(0x30,0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,0x39,0x41,0x42,0x43,0x44,0x45,0x46);
var str = new Array;
for(var i = 0; num > 0; i++){
var tmpNum = num & 0x0F;
str[i] = String.fromCharCode(str16[tmpNum]);
num >>= 4;
}
return str.reverse().join("");
}
function dec2hex5(num){
var str16 = "0123456789ABCDEF";
var str = new Array;
for(var i = 0; num > 0; i++){
var tmpNum = num % 16;
str[i] = str16.charAt(tmpNum);
num >>= 4;
}
return str.reverse().join("");
}
function dec2hex6(num){
var str16 = new Array("0","1","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F");
var str = new Array;
for(var i = 0; num > 0; i++){
var tmpNum = num & 0x0F;
str[i] = str16[tmpNum].charAt(0);
num >>= 4;
}
return str.reverse().join("");
}
function dec2hex7(num){
var str16 = new Array("0","1","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F");
var str = new Array;
for(var i = 0; num > 0; i++){
var tmpNum = num & 0x0F;
if(tmpNum > 9){
str[i] = String.fromCharCode(tmpNum + 0x30);
}else{
str[i] = String.fromCharCode(tmpNum + 0x37);
}
num >>= 4;
}
return str.reverse().join("");
}
function dec2hex8(num){
var str16 = new Array(
String.fromCharCode(0x30),
String.fromCharCode(0x31),
String.fromCharCode(0x32),
String.fromCharCode(0x33),
String.fromCharCode(0x34),
String.fromCharCode(0x35),
String.fromCharCode(0x36),
String.fromCharCode(0x37),
String.fromCharCode(0x38),
String.fromCharCode(0x39),
String.fromCharCode(0x41),
String.fromCharCode(0x42),
String.fromCharCode(0x43),
String.fromCharCode(0x44),
String.fromCharCode(0x45),
String.fromCharCode(0x46));
var str = new Array;
for(var i = 0; num > 0; i++){
var tmpNum = num & 0x0F;
str[i] = str16[tmpNum];
num >>= 4;
}
return str.reverse().join("");
}
function dec2hex9(num){
var str16 = new Array(
"0".charAt(0),
"1".charAt(0),
"1".charAt(0),
"2".charAt(0),
"3".charAt(0),
"4".charAt(0),
"5".charAt(0),
"6".charAt(0),
"7".charAt(0),
"8".charAt(0),
"9".charAt(0),
"A".charAt(0),
"B".charAt(0),
"C".charAt(0),
"D".charAt(0),
"E".charAt(0),
"F".charAt(0));
var str = new Array;
for(var i = 0; num > 0; i++){
var tmpNum = num & 0x0F;
str[i] = str16[tmpNum];
num >>= 4;
}
return str.reverse().join("");
}
function dec2hex10(num){
var str16 = "0123456789ABCDEF";
var str = new Array;
for(var i = 0; num > 0; i++){
var tmpNum = num & 0x0F;
str[i] = str16.substring(tmpNum,tmpNum + 1);
num >>= 4;
}
return str.reverse().join("");
}
function $(str){
return document.getElementById(str);
}
var dateTmp;
function t1(){
dateTmp = new Date().getTime();
for(var i = 0; i < 65536; i++){
dec2hex(i);
}
$("d_t1").innerHTML = (((new Date().getTime()) - dateTmp));
}
function t2(){
dateTmp = new Date().getTime();
for(var i = 0; i < 65536; i++){
dec2hex2(i);
}
$("d_t2").innerHTML = (((new Date().getTime()) - dateTmp));
}
function t3(){
dateTmp = new Date().getTime();
for(var i = 0; i < 65536; i++){
dec2hex3(i);
}
$("d_t3").innerHTML = (((new Date().getTime()) - dateTmp));
}
function t4(){
dateTmp = new Date().getTime();
for(var i = 0; i < 65536; i++){
dec2hex4(i);
}
$("d_t4").innerHTML = (((new Date().getTime()) - dateTmp));
}
function t5(){
dateTmp = new Date().getTime();
for(var i = 0; i < 65536; i++){
dec2hex5(i);
}
$("d_t5").innerHTML = (((new Date().getTime()) - dateTmp));
}
function t6(){
dateTmp = new Date().getTime();
for(var i = 0; i < 65536; i++){
dec2hex6(i);
}
$("d_t6").innerHTML = (((new Date().getTime()) - dateTmp));
}
function t7(){
dateTmp = new Date().getTime();
for(var i = 0; i < 65536; i++){
dec2hex7(i);
}
$("d_t7").innerHTML = (((new Date().getTime()) - dateTmp));
}
function t8(){
dateTmp = new Date().getTime();
for(var i = 0; i < 65536; i++){
dec2hex8(i);
}
$("d_t8").innerHTML = (((new Date().getTime()) - dateTmp));
}
function t9(){
dateTmp = new Date().getTime();
for(var i = 0; i < 65536; i++){
dec2hex9(i);
}
$("d_t9").innerHTML = (((new Date().getTime()) - dateTmp));
}
function t10(){
dateTmp = new Date().getTime();
for(var i = 0; i < 65536; i++){
dec2hex10(i);
}
$("d_t10").innerHTML = (((new Date().getTime()) - dateTmp));
}
</script>
<input type=button onclick="t1();"/><span id="d_t1"></span><br/>
<input type=button onclick="t2();"/><span id="d_t2"></span><br/>
<input type=button onclick="t3();"/><span id="d_t3"></span><br/>
<input type=button onclick="t4();"/><span id="d_t4"></span><br/>
<input type=button onclick="t5();"/><span id="d_t5"></span><br/>
<input type=button onclick="t6();"/><span id="d_t6"></span><br/>
<input type=button onclick="t7();"/><span id="d_t7"></span><br/>
<input type=button onclick="t8();"/><span id="d_t8"></span><br/>
<input type=button onclick="t9();"/><span id="d_t9"></span><br/>
<input type=button onclick="t10();"/><span id="d_t10"></span><br/>
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