js浮点运算式

结果

calc('0.23*-0.03+(4*0.2)') =>0.7931

代码 //加|减|乘|除 浮点运算 const floatMulti = (a, b) => { let m = 0, s1 = a.toString(), s2 = b.toString(), s1l = s1.split('.')[1], s2l = s2.split('.')[1] m = (s1l ? s1l.length : 0) + (s2l ? s2l.length : 0) return Number(s1.replace('.', '')) * Number(s2.replace('.', '')) / Math.pow(10, m) } const floatSub = (a, b) => { let m = 0, s1 = a.toString(), s2 = b.toString(), s1l = s1.split('.')[1], s2l = s2.split('.')[1] m = Math.max((s1l ? s1l.length : 0) ,(s2l ? s2l.length : 0)) return(Number(s1)*Math.pow(10, m) - Number(s2)*Math.pow(10, m)) / Math.pow(10, m) } const floatAdd = (a, b) => { let m = 0, s1 = a.toString(), s2 = b.toString(), s1l = s1.split('.')[1], s2l = s2.split('.')[1] m = Math.max((s1l ? s1l.length : 0) ,(s2l ? s2l.length : 0)) return (Number(s1)*Math.pow(10, m) + Number(s2)*Math.pow(10, m)) / Math.pow(10, m) } const floatDev = (a, b) => { let m = 0, s1 = a.toString(), s2 = b.toString(), s1l = s1.split('.')[1], s2l = s2.split('.')[1] m = (s1l ? s1l.length : 0) + (s2l ? s2l.length : 0) return (Number(s1.replace('.', '')) / Number(s2.replace('.', ''))) / Math.pow(10, m) } /* * 浮点运算式 * */ export const calc = (() => { //一般的算数表达式即为中缀表达式 // let str = "1+((2 + 3 ) * 4 ) - 5 "; //运算符权重 const sdw = { '+': 1, '-': 1, '*': 2, '/': 2 }; //循环安全数 let saveCircle = 137; /** *判断是 运算符|操作数|括号 * 【-】字符前面有任何其他运算符则本身被当作数字一部分 *@return 1:操作数 2:括号 0:运算符 */ const typeChk = (d) => /^-*[\.\d]+$/.test(d) ? 1 : (/[\(\)]/.test(d) ? 2 : 0) /* * 操作符操作方法 * */ const handle = { '+': floatAdd, '-': floatSub, '*': floatMulti, '/': floatDev } /** * 处理输入 * 1) 替换中英括号 * 2) 去除空格 * 3) 小数点前后非数字，则去除 * 3) 小数点之前为空,后面为数字则默认前面添加0 * 4) 返回字符分割 */ const dealStr = (str) => str //替换左右括号 .replace(/（/, '(') .replace(/）/, ')') //替换空字符 .replace(/[^\d\.\(\)\+\*\/-]/g, '') //替换- // .replace(/(\d)-/g,'+-') // .replace(/--/g,'+') // .replace(/-\(/g,'-1*(') // .replace(/-/g,'+-1*') .match(/(((?<=[^\d])-[\.\d]+)+)|(^-[\.\d]+)|([\d\.]+)|([\(\)\+\*\/-])/g) //中缀表达式转前缀表达式并计算 return (str) => { let operand = [];//操作数栈 let operator = [];//操作符栈 //去空格(主要是避免数字被空格拆分),分割成数组 let arr = dealStr(str); // log(arr) //按照规则入栈 let type; for (let i = arr.length - 1, curr; (curr = arr[i]) != null; i--) { type = typeChk(curr); if (type === 1) { operand.push(+curr) } else if (type === 0) { let si = 0, stackTop; while (true && si++ < saveCircle) { stackTop = operator[operator.length - 1]; if (stackTop == null || stackTop === ')') { operator.push(curr); break; } else if (sdw[curr] >= sdw[stackTop]) { operator.push(curr); break; } else { operand.push(operator.pop()) } } } else { if (curr === ')') { operator.push(curr) }else{ let s, si = 0; while (s !== ')' && si++ < saveCircle) { s = operator.pop(); if (s === ')') break operand.push(s) } } } } //将操作符栈中剩下的弹出压入操作数栈 // operand = [...operand, ...operator.reverse()];// num => ["5", "4", "3", "2", "+", "×", "1", "+", "-"] //"1+((2 + 3 ) × 4 ) - 5 " let prevStack = [...operator, ...operand.reverse()];// ["-", "+", "1", "×", "+", "2", "3", "4", "5"] //计算 let resultStack = [], left, right; for (let i = prevStack.length - 1, curr; (curr = prevStack[i]) != null; i--) { if (typeChk(curr)) { //是操作数 resultStack.push(curr) } else { //是操作符 left = resultStack.pop(); right = resultStack.pop(); // console.log(left,right,curr) resultStack.push(handle[curr](left, right)) } } // log(prevStack); //log(resultStack); return resultStack.length != 1 ? '表达式有误' : resultStack[0] } })() 代码 //加|减|乘