软件开发培训班 >> 编程开发 >> JavaScript

js表达式计算器代码

　　本文标签：表达式,计算器

} 
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><br><INPUT onclick=runEx('runcode') type=button value=运行代码 /><br>
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