Adding numbers to array elements

Question

I want to add some number to elements of any array but I get NaN. I know why we have all NaN. Just want to know a way to do something similar.

var a = [];

for(var i=0;i<6;i++){
  for(var j=0;j<2;j++){
    var random_number = Math.floor(Math.random() * 10) + 1;
    a[i] += random_number
  }	
}

console.log(a) //[NaN, NaN, NaN, NaN, NaN, NaN]

Answer 1

+= ... is appending ... to whatever was previously in your variable. Here, it's appending a number to an unset value, giving NaN.

Just get rid of your += when setting your array values :

var a = [];

for(var i=0;i<6;i++){
    for(var j=0;j<2;j++){
        var random_number = Math.floor(Math.random() * 10) + 1;
        a[i] = random_number;
    }   
}

console.log(a)

Answer 2

You could take a default value of zero instead of undefined for addition.

var a = [],
    i, j, random_number;

for (i = 0; i < 6; i++) {
    for (j = 0; j < 2; j++) {
        random_number = Math.floor(Math.random() * 10) + 1;
        a[i] = (a[i] || 0) + random_number;
    }
}

console.log(a)

Answer 3

Just remove '+=' , instead just use '='

You are assigning a number to an unassigned variable. That's why you are getting NaN error.