Refreshing the current variables within a JavaScript array

Question

Refreshing the current variables within a JavaScript array

When I add variables to an array in JavaScript and then update each element, why do the variables all show the same value when outputting them in the console?

In this example, I would anticipate seeing 777 for all variables in the console, but instead they display as 0.

However, when logging the array itself, it correctly shows [777,777,777].

var number1 = 0;
var number2 = 0;
var number3 = 0;

var numbers = [number1, number2, number3];

function updateNumbers() {
  var i;
  for (i = 0; i < numbers.length; i++) {
    numbers[i] = 777;

    console.log(numbers);

    console.log(number1);
    console.log(number2);
    console.log(number3);
  }

}

updateNumbers();

javascript arrays loops for-loop var

Answer 1

Answer №1

When initializing your array, you are assigning the variables by value rather than by reference.

var a = 1;
var b = 2;
var c = 3;
var test = [a, b, c];
console.log(test);

You can achieve similar functionality using objects instead.

var a = {
  value: 1
};
var b = {
  value: 2
};
var c = {
  value: 3
};

var test = [a, b, c];

function updateNumbers() {
  var i;
  for (i = 0; i < test.length; i++) {
    test[i].value = 777;
  }
}

updateNumbers();

console.log(test); // The output will be different from your initial example
console.log(a.value);
console.log(b.value);
console.log(c.value);

Answer 2

When initializing your array, you are assigning the variables by value rather than by reference.

var a = 1;
var b = 2;
var c = 3;
var test = [a, b, c];
console.log(test);

You can achieve similar functionality using objects instead.

var a = {
  value: 1
};
var b = {
  value: 2
};
var c = {
  value: 3
};

var test = [a, b, c];

function updateNumbers() {
  var i;
  for (i = 0; i < test.length; i++) {
    test[i].value = 777;
  }
}

updateNumbers();

console.log(test); // The output will be different from your initial example
console.log(a.value);
console.log(b.value);
console.log(c.value);

Refreshing the current variables within a JavaScript array

Answer №1

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