是的,你可以做到.通过AJAX调用加载CSS文件不是唯一的方法,但它可能是使其真正跨浏览器的唯一(但效率低下)方式.即使下面的声明也不会使它成为真正的跨浏览器,因为calc()函数是not supported by all浏览器,它是一个CSS3功能.

编辑：自2018年起,所有现代浏览器都支持calc.

div {
    width: 300px; /* a fallback value for old browsers */
    width: -webkit-calc(100% - 50px);
    width: -moz-calc(100% - 50px);
    width: calc(100% - 50px);
}

您可以从document.styleSheets及其规则中获取原始CSS代码.规则的cssText属性将为您提供完整的语句.但是不同的浏览器可能会以不同的方式使用calc()函数来解析值.

我将使用更复杂的示例来查看浏览器如何处理calc()函数：

calc(100% - -50px*6 + 4em/2);

这就是Firefox(第18版)对待它的方式：

这就是谷歌Chrome(第24集)对待它的方式：

如图所示; FF按原样获取非前缀的calc值,Chrome获取-webkit前缀值,并使用嵌套括号(如果需要)重新解析它.如果你没有在Chrome中声明它-webkit;它会完全忽略这个价值.因此,我们应该在操作calc语句时考虑这些因素.

现在,使用复杂的例子;我们将首先在calc()函数中获取语句：

"100% - -50px*6 + 4em/2"

然后将语句元素解析为数组：

["100%","-","-50px","*","6","+","4em","/","2"]

最后,处理数组项的值和单位,使它们以编程方式可用(如您所愿)：

[{ value:100,unit:"%" },{ value:-50,unit:"px" },{ value:6,unit:undefined },{ value:4,unit:"em" },{ value:2,unit:undefined }]

上面的最终结果包括值对象和运算符(按顺序).

在进一步阅读之前请注意,以下代码未在所有浏览器和情境中进行完全测试.它不处理嵌套的括号解析(如Chrome所做的)或具有多个或组合calc()函数的值.如果你想测试这个;我推荐Firefox,因为它不解析嵌套的括号,或者你可以扩展代码以支持它们.

// Get the sheet you want to process. (assume we want to process the third sheet):
var sheet = document.styleSheets[2]; //you could also iterate all the sheets in a for loop
processRules(sheet);

/** Iterates through the rules of the specified style sheet;  
 *  then dissolves and logs values including a calc() function.
 */
function processRules(sheet) {
    var rules = sheet.cssRules // Mozilla,Safari,Chrome,Opera
        || sheet.rules; // IE,Safari
    for (var i = 0; i < rules.length; i++) {
        var rule = rules[i];
        // Check if we have a calc() function in this rule
        if (hasCalc(rule.cssText)) {
            // Get the calculation statement inside the calc() function.
            var statement = getCalcStatement(rule.cssText);
            // Dissolve the statement into its elements and log.
            console.log(dissolveCalcElements(statement));
        }
    }
}

/** Checks whether the CSS value includes a calc() function,*  (This is also for avoiding unnecessary regex.)
 */
function hasCalc(value) {
    return value.toLowerCase().indexOf('calc(') >= 0;
}

/** Gets the full statement (string) inside a calc() function.
 */
function getCalcStatement(rule) {
    if (!rule) return '';
    var pattern = /calc\(([^\)]+)\).*/;
    var match = pattern.exec(rule);
    return match && match.length > 1 ? match[1] : '';
}

/** Splits the calc operation's elements (values and operators) and 
 *  dissolves the values into objects with value and unit properties. 
 */
function dissolveCalcElements(statement) {
    // The CSS calc() function supports 4 basic math operations only: 
    // Addition (+),Subtraction (-),Multiplication (*),Division (/)
    // White-spaces are very important in a calc statement. 
    // From Mozilla: "The + and - operators must always be surrounded by whitespace. 
    // The * and / operators do not require whitespace,but adding it for consistency is allowed,and recommended."
    // We could use: statement.split(/(\s+[\+\-]\s+|\s*[\*\/]\s*)/);
    // to include the operators inside the output array,but not all browsers 
    // support splicing the capturing parentheses into the array like that. So:
    statement = statement.replace('*',' * ').replace('/',' / ');
    var arr = statement.split(/\s+/);

    console.log("arr",arr);
    var calcElems = [];
    for (var i = 0; i < arr.length; i++) {
        var d = dissolveElement(arr[i]);
        calcElems.push(d);
    }
    return calcElems;
}

/** Dissolves the value and unit of the element and 
 *  returns either the operator or an object with "value" and "unit" properties.
 */
function dissolveElement(val) {
    // Check if the value is an operator.
    var ops = '+-*/';
    if (ops.indexOf(val) >= 0) return val;

    var o = {};
    // CSS units in a calc statement can have all the regular units. 
    // According to W3C; they can also,can include a "vw" unit (stands for viewport).
    var pattern = /([\+\-]?[0-9\.]+)(%|px|pt|em|in|cm|mm|ex|pc|vw)?/;
    // Exec the value/unit pattern on the property value.
    var match = pattern.exec(val);
    // So we reset to the original value if there is no unit.
    if (match) { 
        var v = match.length >= 2 ? match[1] : match[0];
        o.value = toFloat(v); //parse value as float
        o.unit = match.length >= 3 ? match[2] : '';
    }
    else {
        o = { value:val,unit:''};
    }
    console.log("dissolve",match,val,o);
    return o;
}

// Helper Functions
function toFloat(value) { return parseFloat(value) || 0.0; }

而已.正如我所提到的,我不会这样做,但知道是否有可能,这总是好的.

注意：既然你提到制作一个jQuery插件(为了好玩);你真的不需要jQuery.调用函数如$(‘div’).css(‘width’)只会给你计算值,而不是raw calc语句.