Name variable with a variable

Question

I am trying to get out of this, variables Car1 Car2, Car3, Car4 to be pushed to an array. But I can't seem to figure out how to increment a variable within a for loop. Any ideas?

function get_info() {
 n = 0;
 for (var option_post in postvalues) {
 n++;
 var pair = postvalues[option_post];
 var string_pair = pair.concat(": ")
 var new_postvalues = (string_pair.concat(document.getElementsByName(pair)[0].value));
 //Set up cars
 var make.concat(n) = document.getElementById("make").value;
 var year.concat(n) = document.getElementById("year").value;
 var model.concat(n) = document.getElementById("model").value;
 var car.concat(n) = "Make: ".concat(make.concat(n)).concat("-Model: ").concat(model.concat(n)).concat("-Year:").concat(year.concat(n)); // combine
 }
 cars.push(car1, car2, car3, car4);
}

• das-g: Might you be looking for the array index operator []? E.g. cars.push(car[0], car[1], car[2], car[3]);
• LinuxDisciple: Could you explain what you hope to end up with? It looks like all of your calls to document.getElementById are going to come back the same for each iteration of the for-loop. Is that intentional?
• Blake Connally: @LinuxDisciple Pretty straightforward if you read it, I need the Make, Year, Model for each car in an array.
• trincot: Where are your variables Car1, ... in that piece of code? That (broken) code seems unrelated to your question. Not clear, at least to me.
• Barmar: @trincot He's hoping that var car.concat(n) will declare a variable named car1 when n = 1.

Answer 1

There is no reason to create a new identifier on each loop iteration, especially since you are looking to collect the values into an array.

function get_info() {
 var cars = [], car;
 for (var i = 0; i < postvalues.length; i++) {
 // ...
 // create a car
 car = "Make: " + document.getElementById('make' + i).value
 + "-Model: " + document.getElementById('model' + i).value
 + "-Year: " + document.getElementById('year' + i).value;
 // append it to the end of your array
 cars.push(car);
 }
 return cars;
}

• Blake Connally: This would work but I need to change the ID of the div values. They also need to increment by one. make1, model1, year1, then make2, year2, model, 2
• Igor Raush: What is the type of postvalues? Is it an array?
• Igor Raush: Please see my edit. To iterate over an array, you should be using a plain for loop rather than a for-in loop. This also allows you to use the loop index to generate the <div> IDs.
• Blake Connally: This divs are still not increasing, showing an error each time saying it can't find the div.
• Igor Raush: This means that your <div> IDs are not make1, make2, etc., they are something else. Can you post the HTML you are working with?

Answer 2

I would create an object for each car, and then store them in another object keyed by the car name. Something along these lines:

var cars = {};
for(var i = 0; i < carData.length; i++) {
 var carRef = "car" + n;
 cars[carRef] = {};
 cars[carRef].make = carData[i].make;
 cars[carRef].year = carData[i].year;
 cars[carRef].model = carData[i].model;
}

It's not an exact match to your code, but hopefully you can get the idea from this example. With this, you would retrieve an individual car like this:

cars["car1"]

Or an individual property for a given car:

cars["car1"].make

• Barmar: Instead of an object, use an array cars = [].
• Andrew D: He wants to use strings to reference cars though?
• Barmar: That's just internal to the function, he ends with cars.push(car1, car2, ...)
• Andrew D: Yeah I see that in his example, but I'm not sure if it being an array is necessary to his desired outcome. From the question title I got the impression he wanted to be able to reference "car1", "car2", "car3", etc.
• Barmar: The first sentence of the question say "variables car1, car2, ... to be pushed onto an array"