我想在语法result [3] .column_name中用变量替换列名，以便我可以根据用户进行打印

Question

I am trying to print a specific column of a mysql table told by the user in runtime (without using if else ,which will make code tidious)

var columns = ['D'];

("SELECT ?? FROM money",[columns], function (err, results, fields) 

IN THIS I HAVE TO SPECIFY COLUMN NAME(D) --

results[2].D

OR

var x = String("D") + i.toString();

results[2].x

THIS DIDT WORKED

Answer 1

If you want to access a column by name, but you have the name in a variable, remember JavaScript objects allow access that way:

let column = 'D';
results[2][column] // => D column value

Your var x defines an x variable. This, however:

results[2].x

This looks up a property named literally x on that result.

It's also not clear what the intent behind String("D") is, as "D" is already a string. Making a superstring?

JavaScript has an interpolation system specifically for this:

var x = `D${i}`;