在Javascript中，如何應用動態創建的函數名稱

Question

我的目標是有效地將一組動態選擇的變換應用於矩陣的每個元素。我將選定的函數存儲在一個數組中，然後通過矩陣將它們中的每一個應用於一次。

我的問題是，我該如何動態創建一個函數的名稱，我將它添加到函數數組中？

這個fiddle包含我的嘗試。我的問題包含在評論欄中。

function dynam() { 

    var prepend = 'before - '; 
    var append = ' - after'; 
    var whichCase = 'Upper'; 

    var functionsToApply = []; 
    var matrix = [ 
        ['aBc', 'DeF'], 
        ['ghi', 'JKL'], 
       ]; 

    var out = 'Initial: ' + matrix.join(' | '); 
    document.getElementById('output').innerHTML = out + '\n'; 
    console.log(out); 

    // Set up transforms 
    if (whichCase == 'Lower') { 
    functionsToApply.push(function(v) {return v.toLowerCase();}); 
    } else if (whichCase == 'Upper'){ 
    functionsToApply.push(function(v) {return v.toUpperCase();}); 
    } 

// How can the function be defined dynamically? 
// Perhaps something like: 
// if(['Lower','Upper'].indexOf(whichCase) != -1) { 
// functionsToApply.push(function(v) {'return v.to' + which + 'Case();'}); 
// } 

    if (prepend && prepend.length > 0 && prepend != 'none') { 
    functionsToApply.push(function(v) {return prepend + v;}); 
    } 
    if (append && append.length > 0 && append != 'none') { 
    functionsToApply.push(function(v) {return v + append;}); 
    } 

// Apply all of the transforms to each of the elements of the matrix 
    matrix = matrix.map(function(row){ 
    return row.map(function(val) { 
     for (var fn = 0; fn < functionsToApply.length; fn++) { 
     val = functionsToApply[fn](val); 
     } 
     return val; 
    }) 
    }); 

    out = 'Final: ' + matrix.join(' | '); 
    document.getElementById('output').innerHTML += out + '\n'; 
    console.log(out); 
} 

Answer 1

我喜歡我的聲明功能的哈希在這種情況下，那麼你就可以根據傳遞的價值，這是關鍵的哈希打電話給他們。

更新：我已經添加了一種方法來動態獲取低/高功能，並調用它。

function dynam(whichCase, prepend, append, matrix) { 
 

 
var functionHash = { 
 
    "Lower" : function(v) {return v.toLowerCase();}, 
 
    "Upper" : function(v) {return v.toUpperCase();}, 
 
    "Prepend" : function(v) {return prepend + v;}, 
 
    "Append": function(v) {return v + append;} 
 
} 
 

 
// to actually get the case function based on the word passed in, 
 
// you can do it this way. 
 

 
var lowerUpperFunction = String.prototype['to' + whichCase + 'Case']; 
 
var str = lowerUpperFunction.call("xyz"); 
 
console.log(str); 
 

 
    var functionsToApply = []; 
 
    
 
    var out = 'Initial: ' + matrix.join(' | '); 
 
    console.log(out); 
 
    
 
// see how we just take the whichCase and make that a call to the hash? 
 
functionsToApply.push(functionHash[whichCase]); 
 

 
if (prepend && prepend.length > 0 && prepend != 'none') { 
 
    functionsToApply.push(functionHash["Prepend"]); 
 
    } 
 

 
if (append && append.length > 0 && append != 'none') { 
 
    functionsToApply.push(functionHash["Append"]); 
 
} 
 

 
// Apply all of the transforms to each of the elements of the matrix 
 
    matrix = matrix.map(function(row){ 
 
    return row.map(function(val) { 
 
     for (var fn = 0; fn < functionsToApply.length; fn++) { 
 
     console.log("applying function to val" + val); 
 
     val = functionsToApply[fn](val); 
 
     } 
 
     return val; 
 
    }) 
 
    }); 
 

 
    out = 'Final: ' + matrix.join(' | '); 
 
    return out; 
 
} 
 

 

 
    var p = 'before - '; 
 
    var a = ' - after'; 
 
    var w = 'Upper'; 
 
    var m = [ 
 
      ['aBc', 'DeF'], 
 
      ['ghi', 'JKL'], 
 
     ]; 
 
    
 
console.log(dynam(w, p, a, m));