js 四则表运算解析

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算法

javascript

<html>

<head>

<title>suanshu</title>

var pattBrackets = /\([^\(\)]*\)/gm;

function main () {

var testStr = '1+4+(22+33)*((4+7)/6)+(3*4+(4+5))+100';

//console.log('source:',testStr)

var tempArrBrackes = [];

var temp3MArr = [];

var subArr = [];

var regExpShow = document.getElementById('regExp');

regExpShow.innerHTML = regExpShow.innerHTML + '<br>算式： ' +testStr;

//解析出括号中的内容

while(subArr = testStr.match(pattBrackets)) {

for (var i = 0;i < subArr.length ; i++)

{

var name = getName();

tempArrBrackes.push({name:name, formula:subArr[i].substring(1,subArr[i].length - 1)});

testStr = testStr.replace(subArr[i], name);

}

tempArrBrackes.push({name:getName(), formula:testStr});

//把没有括号的算式的数组解析成 a+b=n的树

for (var i = 0; i < tempArrBrackes.length ; i++)

{

var mArr = getStrByParrt(tempArrBrackes[i].formula, tempArrBrackes[i].name);

if (mArr)

{

temp3MArr = temp3MArr.concat(mArr);

}

//计算并将结果树打印到页面

var tree = getValue(temp3MArr);

for (var key in tree)

{

regExpShow.innerHTML = regExpShow.innerHTML + '<br>'+key+': ' + tree[key].formula + ' = ' +tree[key].value;

}

//解析最简单的计算式 a + b = n

var pattArr = [/n{0,1}\d+\*{1}n{0,1}\d+/

,/n{0,1}\d+\/{1}n{0,1}\d+/

,/n{0,1}\d+\+{1}n{0,1}\d+/

,/n{0,1}\d+\-{1}n{0,1}\d+/];

var pattD = /[\+\-\*\/]/gm;

function getStrByParrt (iStr, iName) {

//console.log('----------------------------:',iStr);

var ret = [];

var subStr = [];

for (var i = 0; i < pattArr.length; i++)

{

while(subStr = iStr.match(pattArr[i])) {

if (iStr.match(pattD).length == 1)

{

ret.push({name:iName, formula:subStr[0]});

break;

}

var name = getName();

ret.push({name:name, formula:subStr[0]});

iStr = iStr.replace(subStr, name);

}

//console.log('pattD',ret.toString())

return ret;

}

// 计算式算值

function getValue (m3Arr) {

var retTree = {};

for (var i = 0; i < m3Arr.length ; i++)

{

var formula = m3Arr[i].formula;

var name = m3Arr[i].name;

var sign = formula.match(pattD)[0];

var params = formula.split(sign);

retTree[name] = {

formula : formula

,value : ''

};

switch(sign){

case '+' : retTree[name].value = getValueFromTree(retTree, params[0]) + getValueFromTree(retTree, params[1]); break;

case '-' : retTree[name].value = getValueFromTree(retTree, params[0]) - getValueFromTree(retTree, params[1]); break;

case '*' : retTree[name].value = getValueFromTree(retTree, params[0]) * getValueFromTree(retTree, params[1]); break;

case '/' : retTree[name].value = getValueFromTree(retTree, params[0]) / getValueFromTree(retTree, params[1]); break;

}

return retTree;

}

// 字符串转数字变量不转

function getValueFromTree(tree, name) {

var value = '';

if (name.indexOf('n') >=0)

{

value = parseFloat(tree[name].value);

} else {

value = parseFloat(name);

}

return value;

}

//取变量名

var nameIndex = 0;

function getName () {

return 'n' + nameIndex++;

}

</script>

</head>

</body>

</html>

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css display 属性的实验

2013-12-24 21:37
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