在Javascript中，如何应用动态创建的函数名称

Question

我的目标是有效地将一组动态选择的变换应用于矩阵的每个元素。我将选定的函数存储在一个数组中，然后通过矩阵将它们中的每一个应用于一次。

我的问题是，我该如何动态创建一个函数的名称，我将它添加到函数数组中？

这个fiddle包含我的尝试。我的问题包含在评论栏中。

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

我喜欢我的声明功能的哈希在这种情况下，那么你就可以根据传递的价值，这是关键的哈希打电话给他们。

更新：我已经添加了一种方法来动态获取低/高功能，并调用它。

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));