js表达式计算器代码

效果图：

代码:

} 
function calcComplex(complexExpression) { 
var arr = new Array(); 
var left = 0; 
var right = 0; 
for (var i = 0; i < complexExpression.length; i++) { 
if (complexExpression.charAt(i) == '(') { 
arr.push(i); 
left++; 
} 
if (complexExpression.charAt(i) == ')') { 
arr.push(i); 
right++; 
} 
} 
if (left != right) { 
throw new Error('括号不匹配！','2'); 
} 
var brackets = complexExpression.replace(/[^$|^$]/g, '');

for (i = 0; i < brackets.length; i++) { 
if (brackets.charAt(i) == "(" && brackets.charAt(i + 1) == ")") { 
var simpleExpression = complexExpression.substr(arr[i] + 1, arr[i + 1] - arr[i] - 1); 
if (calcBasic(simpleExpression)<0) { 
complexExpression = complexExpression.substr(0, arr[i]) + '[' + Math.abs(calcBasic(simpleExpression)) + '' + complexExpression.substr(arr[i + 1] + 1); 
} 
else { 
complexExpression = complexExpression.substr(0, arr[i]) + '' + calcBasic(simpleExpression) + '' + complexExpression.substr(arr[i + 1] + 1); 
} 
complexExpression=calcComplex(complexExpression); 
break; 
} 
} 
return complexExpression; 
} 
function calcBasic(baseExpression) { 
if (baseExpression.charAt(0)=='-') { 
baseExpression = '[' + baseExpression.substr(1); 
} 
var constants = baseExpression.trim().replace(/[\*|\/|\+|\-]/g, ' ').split(/\s+/g); 
for (var index in constants) { 
//只留下符号 
baseExpression = baseExpression.replace(/\s+/g, '').replace(constants[index], '');

//将提取的常量字符串转化为数字 
var item; 
if (constants[index].trim().charAt(0)=='[') { 
item = parseFloat(constants[index].trim().replace('[','-')); 
} 
else { 
item = parseFloat(constants[index].trim()); 
}

if (isNaN(item)) { 
throw new Error('存在非法符号！','0'); 
} 
else { 
constants[index] = item; 
} 
} 
if (constants.length != baseExpression.length + 1) { 
throw new Error('表达式有误！','1'); 
}

for (var i = 0; i < baseExpression.length; i++) { 
switch (baseExpression.charAt(i)) { 
case '*': 
constants.splice(i, 2, constants[i] * constants[i + 1]); 
baseExpression = baseExpression.replace('*', ''); 
i -= 1; 
break; 
case '/': 
if (constants[i + 1] == 0) { 
throw new Error('除数不能为0！'); 
} 
constants.splice(i, 2, constants[i] / constants[i + 1]); 
baseExpression = baseExpression.replace('/', ''); 
i -= 1; 
break; 
default: break; 
} 
} 
for (var j = 0; j < baseExpression.length; j++) { 
switch (baseExpression.charAt(j)) { 
case '+': 
constants.splice(j, 2, constants[j] + constants[j + 1]); 
baseExpression = baseExpression.replace('+', ''); 
j -= 1; 
break; 
case '-': 
constants.splice(j, 2, constants[j] - constants[j + 1]); 
baseExpression = baseExpression.replace('-', ''); 
j -= 1; 
break; 
default: break; 
} 
}

return constants[0]; 
} 
// ]]></ script> 
</p> 
<div style="text-align: center;"><textarea id="txtExpression" style="width: 90%; height: 200px; overflow-y: visible;"></textarea>
 
<div style="width: 90%; margin: 4px auto; text-align: left;"><input id="btnSubit" type="button" onclick="calc()" value="计算" /> <span id="txtResult"></span></div>

[Ctrl+A 全选注:如需引入外部Js需刷新才能执行]

js表达式计算器代码_javascript技巧