javascript - 更有效的字符串创建方式

Question

我有以下对象并需要这个字符串:

product_name,@dummy1,@dummy2,seller_sku,@price,item_quantity,@dummy6,@dummy7,@dummy8,@dummy9,@dummy10,@dummy11,@dummy12,@dummy13,@dummy14,@dummy15,@dummy16,@dummy17,@dummy18,@dummy19,@dummy20,@dummy21,@dummy22,@dummy23,@dummy24,@dummy25,fulfillment_channel

---

{ 
  countFields: 27,
  fields: 
   { product_name: 0,
     seller_sku: 3,
     price: 4,
     item_quantity: 5,
     fulfillment_channel: 26 
   } 
}

对象和字符串(包括长度)可能会发生变化。

我这样创建字符串(使用 lodash):

function tableString(fields){
    var obj = _.invert(fields.fields);
    obj.length = fields.countFields;
    var values = Array.prototype.slice.apply( obj );
    var arr = _.merge(new Array(fields.countFields),values).map(function(val,i){
        if (val == 'price' || !~values.indexOf(val)) {
            if (val == 'price') {
                return '@price';
            }
            return '@dummy' + i;
        }
        return val;
    }); 

    return arr.join(',');
}

var first = { 
  countFields: 27,
  fields: {
     product_name: 0,
     seller_sku: 3,
     price: 4,
     item_quantity: 5,
     fulfillment_channel: 26 
  } 
}
                                                              
console.log(tableString(first));

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/3.10.1/lodash.min.js"></script>

我想避免在末尾使用 map()/array 函数。有人找到一种更简单的方法来从对象创建上面的字符串吗？

Answer 1

我不知道这是否更容易，但你会在末尾得到一个字符串和它的普通 javascript。

function tableString(fields){
    var reversedFields = {};
    for(var key in fields.fields){ // we swapped key and value
        reversedFields[fields.fields[key]] = key;
    }

    for(var i=0,x=fields.countFields-1,result = "";i<fields.countFields;i++){
        if(reversedFields[i]){
            result += (reversedFields[i] == 'price' ? '@price' : reversedFields[i]);
        } else {
            result += '@dummy' + i;
        }
        if(i < x){
            result += ",";
        }
    }

    return result;
}

var res = tableString({
    countFields: 27,
    fields:{
        product_name: 0,
        seller_sku: 3,
        price: 4,
        item_quantity: 5,
        fulfillment_channel: 26
    }
});

// result product_name,@dummy1,@dummy2,seller_sku,@price,item_quantity,@dummy6,@dummy7,@dummy8,@dummy9,@dummy10,@dummy11,@dummy12,@dummy13,@dummy14,@dummy15,@dummy16,@dummy17,@dummy18,@dummy19,@dummy20,@dummy21,@dummy22,@dummy23,@dummy24,@dummy25,fulfillment_channel