How to append object value using for loop in javascript?

Question

I loop through an array called accData and make a new array called WL and RF. I want to make it easy to maintain, but I have a problem. When I want to change the WL array data to CH2 and RF array data to DIG2, I have to type the script manually. This is my script

const accData = [
    { st: 'serijabo', path: 'serijabo.json', wl: 'CH1', rf: 'DIG1' },
    { st: 'sukabumi', path: 'sukabumi.json', wl: 'CH2', rf: 'DIG2' },
];

for (let i = 0; i < accData.length; i++) {
  const xhr = new XMLHttpRequest();
  xhr.onreadystatechange = function () {
  if (xhr.readyState === 4) {
    const data = JSON.parse(xhr.responseText);

    let WL = [];
    let RF = [];
    for (let i = 0; i < data.length; i++) {
      WL.push(Number(data[i].CH1)); // this line
      RF.push(Number(data[i].DIG1)); // and this line
    }
  }
 }
}

I try to use ES6 template to solve it but it is not working because the template must be place in a string.

WL.push(Number(data[i].`${accData[i].wl}`)); //not working
RF.push(Number(data[i].`${accData[i].rf}`)); //not working

How can I solve this?

Possible duplicate of JavaScript object declaration syntax - variable names as properties — r3wt
– r3wt, Commented Aug 30, 2019 at 18:07
yes, because json returns string and i want to process number, so i convert it @Vilx- — Waloy
– Waloy, Commented Aug 30, 2019 at 18:08
duplicate of stackoverflow.com/questions/11043026/… and so many hundreds of other questions about the same thing. — r3wt
– r3wt, Commented Aug 30, 2019 at 18:08

Telmo Trooper · Accepted Answer · 2019-08-30 17:55:38Z

0

Have you tried using brackets instead of a dot? They should allow you to access properties via a string.

WL.push(Number(data[i][`${accData[i].wl}`]));
RF.push(Number(data[i][`${accData[i].rf}`]));

answered Aug 30, 2019 at 17:55

Telmo Trooper

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14 Comments

Vilx- Over a year ago

Also i has been redefined in the callback.

Vilx- Over a year ago

Not to mention the whole string expression is totally unnecesary. Just do data[i][accData[i].rf]

Waloy Over a year ago

the data[i][accData[i].wl] returns error "Uncaught TypeError: Cannot read property 'wl' of undefined" while the data[i].CH1 works fine

Telmo Trooper Over a year ago

If you're getting that error it means the object accData[i] doesn't exist at some moment for you to access its wl property. You can write accData[i] && WL.push(Number(data[i][`${accData[i].wl}`])); so the code will only run when accData[i] exists.

Waloy Over a year ago

and the (data[i]['{accData[i].wl}']) returns NaN for every element

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