使用正則表達式和JavaScript獲取字符串中的完全匹配

Question

我試圖從給定的字符串中獲得完全匹配的內容，然后操縱該字符串。 我有一個相當大的計算器程序，您可以在這里看到： http : //www.marcusparsons.com/projects/calculator 。 主頁上還沒有任何內容，並且原始代碼很長。

目標是在計算器中實現一個功能，其中不必在數學對象/方法之前添加數學前綴。 在我添加了一個允許用戶使用“ acosh（）”方法（和實驗方法）的功能之前，無論它是否在瀏覽器中實現（ehem ... IE），它的作用都很大。 我遇到的問題是我現在要用aMath.cosh（）“替換” acosh“的算法，因為它在” acosh“內看到” cos“。

因此，當我將字符串“ acosh（1）+ cos（pi / 3）”傳遞給它時，它變成了“ aMath.cosh（1）+ cos（Math.PI / 3）”。

編輯：上面的字符串應為“ acosh（1）+ Math.cos（Math.PI / 3）”。

我是正則表達式的新手，我想這就是我的問題所在。

這是示例代碼： http : //jsfiddle.net/mparson8/2ej5n3u4/4/

var $mathKeywords = ["E", "LN2", "LN10", "LOG2E", "LOG10E", "PI", "SQRT1_2", "SQRT2", "abs", "acos", "asin", "asinh", "atan", "atan2", "atanh", "cbrt", "ceil", "clz32", "cos", "exp", "expm1", "floor", "fround", "hypot", "imul", "log1p", "log10", "log2", "max", "min", "pow", "random", "round", "sin", "sinh", "sqrt", "tan", "tanh", "trunc"];

var $resultVal = "acosh(1)+cos(PI/3)".toLowerCase();
try {
//Iterate over each Math object/method
$.each($mathKeywords, function (i, val) {
    //Convert val within array to a lower case form
    var $lowerKey = val.toLowerCase();
    //The regex pattern I came up with
    var pattern = new RegExp("(^|\\W)" + $lowerKey + "($|\\W)");
    //See if pattern gives a match within $resultVal
    var $location = $resultVal.match(pattern);
    //Math keyword is found
    if ($location != null) {
        //replace the lowercase version of the math keyword with its properly cased version prepended 
        //with Math. i.e. cos becomes Math.cos and pi becomes Math.PI
        $resultVal = $resultVal.replace($lowerKey, "Math." + val);
    }
});
//Set the result element's value to an evaluation of $resultVal
//A better implementation of the eval exists within the calc program
alert($resultVal);
alert(eval($resultVal));
} catch (err) {
alert("Error: Cannot process expression due to " + err + ".");
}

非常感謝您的幫助！ :)

Answer 1

如果您想繼續使用正則表達式，這似乎可行：

var $mathKeywords = ["E", "LN2", "LN10", "LOG2E", "LOG10E", "PI", "SQRT1_2", "SQRT2", "abs", "acos", "asin", "asinh", "atan", "atan2", "atanh", "cbrt", "ceil", "clz32", "cos", "exp", "expm1", "floor", "fround", "hypot", "imul", "log1p", "log10", "log2", "max", "min", "pow", "random", "round", "sin", "sinh", "sqrt", "tan", "tanh", "trunc"];

var $resultVal = "acosh(1)+cos(PI/3)".toLowerCase();
try {
    //Iterate over each Math object/method
    $.each($mathKeywords, function (i, val) {
        //Convert val within array to a lower case form
        var $lowerKey = val.toLowerCase();
        var pattern = new RegExp("\\b" + $lowerKey + "\\b", "g");
        //See if pattern gives a match within $resultVal
        var $location = $resultVal.match(pattern);
        //Math keyword is found
        if ($location != null) {
            //replace the lowercase version of the math keyword with its properly cased version prepended 
            //with Math. i.e. cos becomes Math.cos and pi becomes Math.PI
            $resultVal = $resultVal.replace(pattern, "Math." + val);
        }
    });
    //Set the result element's value to an evaluation of $resultVal
    //A better implementation of the eval exists within the calc program
    console.log($resultVal);
    console.log(eval($resultVal));
} catch (err) {
    alert("Error: Cannot process expression due to " + err + ".");
}

輸出：

acosh(1)+Math.cos(Math.PI/3)

（實際上它的Error: Cannot process expression due to ReferenceError: acosh is not defined.但是您明白了）

---

變化：

• 使用\\b作為單詞邊界
• 在替換中使用模式（帶有單詞邊界）
• 使用g標志替換所有出現的事件。