How to make a user input into variable name?

Question

I need help with a specific piece of code. It is kind of difficult to describe, but I'll try to do it the best I can. I need to check a specific attribute of an object based on user input. For example, if the user inputs 'London', I want to be able to access an attribute called 'xcoor.london'.

Before I have tried a lot of 'if' and 'else if', for example,

xcoordinate = xcoor.london;
ycoordinate = ycoor.london;
}else if(input == 'Paris'){
xcoordinate = xcoor.paris;
ycoordinate = ycoor.paris;
}else if(input == 'Washington D.C.'){
xcoordinate = xcoor.washdc;
ycoordinate = ycoor.washdc;
}
"But I have dozens of inputs and this takes a lot of code. 
I am just revising this program to make it take up less space, 
and this part is the major problem.
I want something like this:"
var xcoor = {
london: 0.1278,
paris: 2.3522,
...
}
var input = document.getElementById('input').value;
xcoordinate = xcoor.input;

That's pretty much all; any ideas are welcome and appreciated! Thanks in advance!

xcoordinate = xcoor[input];

Keith
– Keith

2019-07-24 12:26:49 +00:00
Commented Jul 24, 2019 at 12:26 — Keith
– Keith, Commented Jul 24, 2019 at 12:26

StefanN · Accepted Answer · 2019-07-24 12:26:54Z

1

I would make a dictionary for the coordinates. Like this:

const coordinates = {
"London": {x: ..., y: ...},
"Paris": {x: ..., y: ...}
};

console.log('The coordinates for London: ',coordinates['London']);
console.log('The x coordinate for Paris: ', coordinates['Paris'].x);

If you want to use your input var to find the coordinates, you can do it like this:

const result = coordinates[input];
console.log(result.x, result.y) //returns the x and y coordinates for the user input

answered Jul 24, 2019 at 12:26

StefanN

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Comments

Nguyễn Hoàng Đông Phương · Accepted Answer · 2019-07-24 12:35:47Z

1

var input = document.getElementById('input').value;
xcoordinate = xcoor[input.toLowerCase()];

With a map object, it will save alot of if else

var map = {
     'washington d.c.': 'washdc',
     'las vegas': 'lasvegas'
};
var input = document.getElementById('input').value;
xcoordinate = xcoor[map[input.toLowerCase()] || input.toLowerCase()];

edited Jul 24, 2019 at 12:35

answered Jul 24, 2019 at 12:27

Nguyễn Hoàng Đông Phương

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2 Comments

Jb31 Over a year ago

Note that this doesn't work out of the box as "Washington D.C." should be stored in xcor["washdc"] not in xcor["washington d.c."], so you will need some kind of mapping.

Nguyễn Hoàng Đông Phương Over a year ago

Yes, he will need a map object anyway.

debugmode · Accepted Answer · 2019-07-24 12:39:26Z

I would like to solve it using the object as shown below,

var xcolor = {
london: 0.1278,
paris: 2.3522,
// keep adding more values here 

}

var ycolor = {
    london: 0.9,
    paris : 10
    // keep adding more values here 
}

let  coordinates = {
    xcoordinate : undefined,
    ycoordinate : undefined 
}



function setInput(input){

  if(xcolor.hasOwnProperty(input) && ycolor.hasOwnProperty(input)){
    coordinates.xcoordinate = xcolor[input];
    coordinates.ycoordinate = ycolor[input];
  }
}

setInput('paris');

console.log(coordinates.xcoordinate);
console.log(coordinates.ycoordinate);

setInput('london');
console.log(coordinates.xcoordinate);
console.log(coordinates.ycoordinate);

I hope it helps

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