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MathUtil.html
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MathUtil.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>加减乘除四则运算</title>
</head>
<body>
<a href="http://www.jb51.net/article/85463.htm" target="_blank">参考资料</a>
<p>parseInt函数官方解释说是将字符串转化为数字，事实上证明它可以将字符串或者数字 转化为数字</p>
<script>
// 1.功能：字符串之间的数字运算
/*
* 整体思路：小数进行四则运算时，会出现精度损失问题，而整数则没有这种问题。
* 所以先将小数转化为整数进行四则运算，再将整数转化为小数
* @param c,d 字符串数值
* @param n 运算类型： 0为+ 1为- 2为乘 3为除
*/
function executeStr(c, d, n) {
// 去掉空相
var re = /\s/g;
var a = c.replace(re, "");
var b = d.replace(re, "");
var cutN = "10000000000000";
var cutZero = "00000000000";
var dot = ".";
// 将小数输入为整数
var adot = a.indexOf(dot) > 0 ? a.length - a.indexOf(dot) : 0;
var bdot = b.indexOf(dot) > 0 ? b.length - b.indexOf(dot) : 0;
var cutA = adot > 0 ? parseInt(cutN.substr(0, adot)) : 1;
var cutB = bdot > 0 ? parseInt(cutN.substr(0, bdot)) : 1;
var maxcutAB = Math.max(cutA, cutB);
var mincutAB = Math.min(cutA, cutB);
var cutAB = maxcutAB / mincutAB;
var numA = 0;
var numB = 0;
var inzero = cutZero.substr(0, cutAB.toString().length - 1);
var cutLen = maxcutAB.toString().length - 1;
if (adot == bdot) {
numA = parseInt(a.replace(dot, ""), 10);
numB = parseInt(b.replace(dot, ""), 10);
} else if (adot > bdot) {
numA = parseInt(a.replace(dot, ""), 10);
numB = parseInt(b.replace(dot, "") + inzero, 10);
} else {
numB = parseInt(b.replace(dot, ""), 10);
numA = parseInt(a.replace(dot, "") + inzero, 10);
}
var numAB = "0.0";
var lastN = "0.0";
switch (n) {
case 0:
// 加
numAB = ((numA + numB) / maxcutAB).toString();
break;
case 1:
// 减
numAB = ((numA - numB) / maxcutAB).toString();
break;
case 2:
// 乘
numAB = Math.abs(numA * numB).toString();
cutLen = cutLen * 2;
break;
case 3:
// 除
numAB = (numA / numB).toString();
break;
}
// 对乘法的特别处理
if (n == 2) {
if (numAB.length <= cutLen) {
numAB = cutZero.substr(0, cutLen - numAB.length + 1) + numAB;
}
if (Math.abs(numA * numB) != numA * numB) {
numAB = "-" + numAB;
}
numAB = numAB.slice(0, numAB.length - cutLen) + "." + numAB.slice(numAB.length - cutLen);
}
return parseFloat(numAB).toString();
}
// 测试1
// console.log(executeStr('1.331', '0.004', 0));
// console.log(executeStr('1.336', '0.001', 1));
// console.log(executeStr('13.35', '0.1', 2));
// console.log(executeStr('133.5', '100', 3));
// 2. 字符串或者数字之间进行四则运算，且可以保留小数位
/**
* @param x 运算数
* @param y 运算数
* @param op 操作符，0：加；1：减；2：乘；3：除
* @param acc 保留小数位个数，进行四舍五入
*/
function execute(x, y, op, acc) {
// ???此处存在争议，如果用户输入的为undefined，是将其转换为0,还是将这个错误抛出来?
var xx = Number(x == undefined ? 0 : x);
var yy = Number(y == undefined ? 0 : y);
var a = science(xx);
var b = science(yy);
var na = a.num;
var nb = b.num;
var ta = a.times;
var tb = b.times;
var maxt = ta > tb ? ta : tb;
var result = 0;
switch (parseInt(op, 10)) {
case 0:
// 加
if (ta == tb) {
result = na + nb;
} else if (ta > tb) {
result = na + nb * (ta / tb);
} else {
result = na * (tb / ta) + nb;
}
result = result / maxt;
break;
case 1:
// 减
if (ta === tb) {
result = na - nb;
} else if (ta > tb) {
result = na - nb * (ta / tb);
} else {
result = na * (tb / ta) - nb;
}
result = result / maxt;
break;
case 2:
// 乘
result = na * nb / (ta * tb);
break;
case 3:
// 除
var nab = na / nb;
var tab = tb / ta;
return execute(nab, tab, 2, acc);
}
if (acc != undefined && acc != null) {
// ???原生JS函数存在精度损失bug
// return Number(Number(result).toFixed(parseInt(acc)));
return Number(toFixed(Number(result),parseInt(acc)));
} else {
return Number(result);
}
}
/**
* 科学计数法
*
* @param num
* @returns
*/
function science(num) {
var re = {
num: 0,
times: 1
};
if (isInteger(num)) {
re.num = num;
return re;
}
var snum = num + "";
var dotPos = snum.indexOf(".");
var len = snum.substr(dotPos + 1).length;
var times = Math.pow(10, len);
var intNum = parseInt(snum.replace(".", ""));
re.times = times;
re.num = intNum;
return re;
}
/**
* 判断是否为整数，字符整数也返回true
*
* @param num
* @returns
*/
function isInteger(num) {
return Math.floor(num) === Number(num);
}
// // toFixed 修复 原生JS函数存在精度损失bug
// 该函数存在两个bug
// 1.num为负数时，四舍五入报错
// 2.num为整数时，不能补0
// function toFixed(num, s) {
// var times = Math.pow(10, s)
// // var des = num * times + 0.5;
// var des = (num + '').replace('.','');
// des = parseInt(des, 10) / times
// return des + ''
// }
/*
* 稍有不同的是 js的toFixed在保留位数不够的情况下会自动补零
* 因此加了第三个参数，是否补零，默认是补零的--
*/
function toFixed(num, s, f) {
var ff = typeof (f) == "undefined" ? true : f;
var times = Math.pow(10, s);
var des = num * times + (num >= 0 ? 0.5 : -0.5);
des = parseInt(des, 10) / times;
des += '';
if (ff) {
if (des.indexOf(".") == -1) {
for (var i = 0; i < s; i++) {
if (i == 0) des += ".";
des += "0";
}
} else {
var dotPos = des.indexOf('.')
var len = des.substr(dotPos + 1).length
if (len < s) {
for (var i = 0; i < s - len; i++) {
des += "0";
}
}
}
return des;
} else {
return des;
}
}
// 测试2
console.log(execute('1.331', '0.004', 0,2));
console.log(execute('1.336', '0.001', 1,2));
console.log(execute('13.35', '0.1', 2,2));
console.log(execute('133.5', '100', 3,2));
</script>
</body>
</html>