更有效的字符串创建方式

Question

I have the following object and need this string:

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 
   } 
}

The object and the string (including length) are subject to change.

I create the string like this (using 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> 

I would like to avoid the map() /array functions at the end. Does someone find an easier way to create above string from the object?

Answer 1

I don't know if this is easier but you get a string at the end and its vanilla 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