I am trying to store values in array using JavaScript, but I get strange error:

let a = 1;
for (i = 0; i < 4; i++) {

  var all = new Array();
  all[i] = a;
  a++;
}

console.log(all[1]);
console.log(all[2]);
console.log(all[3]);

I am trying to store values in array using JavaScript, but I get strange error:

let a = 1;
for (i = 0; i < 4; i++) {

  var all = new Array();
  all[i] = a;
  a++;
}

console.log(all[1]);
console.log(all[2]);
console.log(all[3]);

For all[1] and all[2] I am getting undefined error, but all[3] is working fine.

• javascript

9 Answers 9

You are reassigning your array in every loop iteration (which deletes everything in it) instead of only before the whole loop.

This should work as expected:

var a = 1;
var all = new Array();
for(i=0;i<4;i++)
{
    all[i]=a;
    a++;
}

alert(all[1]);
alert(all[2]);
alert(all[3]);

You are re-initializing the array inside of the for-loop, overwriting any data you had previously written. Move new Array() (or better [], the array literal) outside the loop

 var all = [];
    for (i = 0; i <= 4; i++) {
      let element = i;
      all.push(element);
    }
    alert(all[1]);
    alert(all[2]);
    alert(all[3]);
    alert(all[4]);

You are recreating the array on each iteration. Try this:

var all = []; // Moved up, and replaced with bracket notation.
var a = 1;
for(i=0;i<4;i++)
{
all[i]=a;
a++;
}

alert(all[1]);
alert(all[2]);
alert(all[3]);

Your issue here is that you're reinstantiating a new Array on each iteration of the loop. So, the first time around, you set a value in that array. The second time around, you redefine the all variable to be a completely new array, which undoes the work you did in the last iteration.

The easiest thing to do is just move var all = new Array() and put it before your loop.

You are redefining your array inside the for loop. You need to define it outside.

var a = 1;
var all = new Array();
for(i=0;i<4;i++)
{
  all[i]=a;
  a++;
}

alert(all[1]);
alert(all[2]);
alert(all[3]);

var a = 1;
var all = new Array();
for(i=0;i<4;i++)
{


all[i]=a;
a++;
}

alert(all[0]);
alert(all[1]);
alert(all[2]

You need to put var all = new Array() outside your loop. You're creating a new all[] four times.

var a = 1;
var all = new Array();
for(i=0;i<4;i++)
{
   all[i]=a;
   a++;
}

alert(all[1]);
alert(all[2]);
alert(all[3]);

Try some thing like:

const Coin = [
  "Heads",
  "Tails"];