Concatenation doesn't seem to work in JavaScript

Question

I am doing something like this in my application. I have sequence of Id values like ID1, ID2 etc. I am trying to fetch the ID value using for loop.

Concatenation doesn't seem to work.

function Save(count,Id1,Id2,Id3){
  var response = [];
  for(var i=1;i <= count; i++) {
    value = `${'Id' + i}`;
    alert(value);
  }
}

<input type="button" value="Submit" onclick="Save(3,1,2,3)" />

Answer 1

You're creating a String "Id1", you cannot interpolate a variable name. But with ES6, you can use the rest parameters (...) to convert parts of your arguments to an Array:

function Save(count, ...ids) {
  var response = [];
  for (var i = 0; i < count; i++) {
    value = ids[i];
    alert(value);
  }
}

<input type="button" value="Submit" onclick="Save(3,1,2,3)" />

Before ES6, you would have to use arguments (that would convert all arguments):

function Save() {
  var response = [];
  for (var i = 1; i <= arguments[0]; i++) {
    value = arguments[i];
    alert(value);
  }
}

<input type="button" value="Submit" onclick="Save(3,1,2,3)" />

Or use eval, but don't. This is just for the example:

function Save(count, Id1, Id2, Id3, Id4) {
  var response = [];
  for (var i = 1; i <= count; i++) {
    value = eval(`Id${i}`);
    alert(value);
  }
}

<input type="button" value="Submit" onclick="Save(3,1,2,3)" />