js开根号用什么函数
js实现开根号计算器输入，js开根号用什么函数教程如下：
输入一个数字
计算结果：得出开根号结果
js实现代码：
<!-- // Javascript scientific calculator (4 March 1996)
// (C) Copyright Rolf Howarth 1996
// rolf@insect.demon.co.uk
var NDIGITS = 16;
var STACKSIZE = 12;
var value = 0;
// current value in display
var memory = GetCookie("CalcMemory");
// current value in memory
if (!memory) memory = 0;
var level = 0;
// no. of items on stack
var entered = true;
// has value on display been 'entered'?
var decimal = 0;
// multiplier when entering after decimal point
var fixed = 0;
// force trailing zero display when entering decimals
var exponent = false;
// currently entering exponent?
var inverse = false;
// has the INV key been pressed?
if (location.search) {
// pass in value through command line
value = location.search.substring(1,location.search.length);
}
function stackItem() {
this.value = 0;
this.op = "";
}
function array(length) {
this[0] = 0;
for (i=0; i<length; ++i)
{
this[i] = 0;
this[i] = new stackItem();
}
this.length = length;
} stack = new array(STACKSIZE);
function push(value,op,prec) {
if (level==STACKSIZE)
return false;
for (i=level;i>0; --i)
{
stack[i].value = stack[i-1].value;
stack[i].op = stack[i-1].op;
stack[i].prec = stack[i-1].prec;
} stack[0].value = value;
stack[0].op = op;
stack[0].prec = prec;
++level;
return true;
}
function pop() {
if (level==0)
return false;
for (i=0;i<level; ++i) {
stack[i].value = stack[i+1].value;
stack[i].op = stack[i+1].op;
stack[i].prec = stack[i+1].prec;
} --level;
return true;
}
function format(value) {
var valStr = "" + value;
if (valStr.indexOf("N")>=0 || (value == 2*value && value == 1+value))
return "Error ";
var i = valStr.indexOf("e")
if (i>=0)
{
var expStr = valStr.substring(i+1,valStr.length);
if (i>11) i=11; // max 11 digits
valStr = valStr.substring(0,i);
if (valStr.indexOf(".")<0) valStr += ".";
valStr += " " + expStr;
}
else
{
var valNeg = false;
if (value < 0)
{ value = -value; valNeg = true;
}
var valInt = Math.floor(value);
var valFrac = value - valInt;
var prec = NDIGITS - (""+valInt).length - 1;
// how many digits available after period
if (! entered && fixed>0)
prec = fixed;
var mult = " 1000000000000000000".substring(1,prec+2);
var frac = Math.floor(valFrac * mult + 0.5);
valInt = Math.floor(Math.floor(value * mult + .5) / mult);
if (valNeg) valStr = "-" + valInt;
else
valStr = "" + valInt;
var fracStr = "00000000000000"+frac;
fracStr = fracStr.substring(fracStr.length-prec, fracStr.length);
i = fracStr.length-1;
if (entered || fixed==0)
{
// remove trailing zeros unless fixed during entry.
while (i>=0 && fracStr.charAt(i)=="0")
--i;
fracStr = fracStr.substring(0,i+1);
} if (i>=0) valStr += "." + fracStr;
// document.result.debugField.value = "prec "+prec+", mult "+mult+", frac "+frac;
} return valStr;
}
function refresh()
{
var display = format(value);
if (exponent)
{
if (expval<0)
display += " " + expval;
else
display += " +" + expval;
}
if (display.indexOf(".")<0 && display != "Error ")
{
if (entered || decimal>0)
display += '.';
else
display += ' ';
}
display = " " + display;
display = display.substring(display.length-NDIGITS-1,display.length);
document.result.result.value = display;
inverse = false;
}
function clearAll() {
level = 0; clear();
}
function clear() {
exponent = false;
value = 0;
enter();
refresh();
}
function evalx() {
if (level==0)
return false;
op = stack[0].op;
sval = stack[0].value;
// alert("eval "+sval+op+value);
if (op == '+')
value = parseFloat(sval) + value;
else if (op == '-')
value = sval - value;
else if (op == '*')
value = sval * value;
else if (op == '/')
value = sval / value;
else if (op == 'pow')
value = Math.pow(sval,value);
pop();
if (op=='(')
return false;
return true;
}
function openp() {
enter();
if (!push(0,'(',0))
{
value = "NAN";
}
refresh();
}
function closep() {
enter();
while (evalx())
;
refresh();
}
function operator(op) {
enter();
if (op=='+' || op=='-') prec = 1;
else if (op=='*' || op=='/') prec = 2;
else if (op=="pow") prec = 3;
if (level>0 && prec <= stack[0].prec) evalx();
if (!push(value,op,prec)) { value = "NAN";
} refresh();
} function enter() { if (exponent) value = value * Math.exp(expval * Math.LN10);
entered = true; exponent = false;
decimal = 0; fixed = 0;
}
function equals() {
enter();
while (level>0)
evalx();
refresh();
}
function digit(n) {
if (entered) {
value = 0;
digits = 0;
entered = false;
}
if (n==0 && digits==0) {
refresh();
return; }
if (exponent) {
if (expval<0)
n = -n;
if (digits < 3)
{
expval = expval * 10 + n;
++digits;
refresh();
}
return;
}
if (value<0)
n = -n;
if (digits < NDIGITS-1) {
++digits;
if (decimal>0) { decimal = decimal * 10;
value = value + (n/decimal); ++fixed;
} else value = value * 10 + n;
} refresh();
} function sign() { if (exponent) expval = -expval;
else value = -value;
refresh(); }
function period() {
if (entered) {
value = 0;
digits = 1;
}
entered = false;
if (decimal == 0) {
decimal = 1;
}
refresh();
} function exp() {
if (entered || exponent)
return;
exponent = true;
expval = 0;
digits = 0;
decimal = 0;
refresh(); }
function inv() {
inverse = !inverse;
}
function func(f) {
enter();
if (f=="1/x")
value = 1/value;
else if (f=="swap")
{
var tmp = value;
value = stack[0].value;
stack[0].value = tmp;
}
else if (f=='n!')
{
if (value<0 || value>200 || value != Math.round(value))
value = "NAN";
else
{
var n = 1;
var i;
for (i=1;i<=value;++i)
n *= i;
value = n;
}
}
else if (f=="MR")
value = memory;
else if (f=="M+")
{
memory += value;
SetCookie("CalcMemory", memory);
}
else if (f=="Min")
{
memory = value;
SetCookie("CalcMemory", memory);
}
else if (inverse)
{
if (f=="sin")
value = Math.asin(value)*180/Math.PI;
else if (f=="cos")
value = Math.acos(value)*180/Math.PI;
else if (f=="tan")
value = Math.atan(value)*180/Math.PI;
else if (f=="log")
value = Math.exp(value * Math.LN10);
else if (f=="log2")
value = Math.exp(value * Math.LN2);
else if (f=="ln")
value = Math.exp(value);
else if (f=="sqrt")
value = value*value;
else if (f=="pi")
value = Math.E;
}
else
{
if (f=="sin")
value = Math.sin(value/180 * Math.PI);
else if (f=="cos")
value = Math.cos(value/180 * Math.PI);
else if (f=="tan")
value = Math.tan(value/180 * Math.PI);
else if (f=="log")
value = Math.log(value)/Math.LN10;
else if (f=="log2")
value = Math.log(value)/Math.LN2;
else if (f=="ln")
value = Math.log(value);
else if (f=="sqrt")
value = Math.sqrt(value);
else if (f=="pi")
value = Math.PI;
}
refresh();
}
function hex() {
location = "calc_hex.html?"+value;
}
/ // // Cookie Functions - Second Helping (21-Jan-96)
// Written by: Bill Dortch, hIdaho Design <bdortch@netw.com>
// The following functions are released to the public domain.
//
function getCookieVal (offset) {
var endstr = document.cookie.indexOf (";", offset);
if (endstr == -1) endstr = document.cookie.length;
return unescape(document.cookie.substring(offset, endstr));
} function GetCookie (name) { var arg = name + "=";
var alen = arg.length; var clen = document.cookie.length;
var i = 0; while (i < clen) { var j = i + alen;
if (document.cookie.substring(i, j) == arg) return getCookieVal (j);
i = document.cookie.indexOf(" ", i) + 1;
if (i == 0) break;
} return null;
}
// Function to create or update a cookie.
// name - String object object containing the cookie name.
// value - String object containing the cookie value. May contain
// any valid string characters.
// [expires] - Date object containing the expiration data of the cookie. If
// omitted or null, expires the cookie at the end of the current session.
// [path] - String object indicating the path for which the cookie is valid.
// If omitted or null, uses the path of the calling document.
// [domain] - String object indicating the domain for which the cookie is
// valid. If omitted or null, uses the domain of the calling document.
// [secure] - Boolean (true/false) value indicating whether cookie transmission
// requires a secure channel (HTTPS).
//
function SetCookie (name, value) { var argv = SetCookie.arguments;
var argc = SetCookie.arguments.length;
var expires = (argc > 2) ? argv[2] : null;
var path = (argc > 3) ? argv[3] : null;
var domain = (argc > 4) ? argv[4] : null;
var secure = (argc > 5) ? argv[5] : false;
document.cookie = name + "=" + escape (value) + ((expires == null) ? "" : ("; expires=" + expires.toGMTString())) + ((path == null) ? "" : ("; path=" + path)) + ((domain == null) ? "" : ("; domain=" + domain)) + ((secure == true) ? "; secure" : "");
}
function DeleteCookie (name) {
var exp = new Date();
exp.setTime (exp.getTime() - 1);
// This cookie is history
var cval = GetCookie (name);
document.cookie = name + "=" + cval + "; expires=" + exp.toGMTString();
}
//
// End of cookie functions //
// -->
实现效果：开根号计算器
参考文章：http://www.itmacom.com/gl/33477.html
