Javascript assigning values into Muti Dimensional array

Question

Using Javascript, I need to create a matrix table that looks like the matrix below:

The following code, to me, seems like that should be correct, however when I try to output arr[0][1] etc... no value show. Did I do something wrong in the following code:

var address = [
"...",
"....",
".....",
"......"

];

var arr = [];

for (i = 0; i < address.length; i++) 
{ 
    for (j = 0; j < address.length; j++) 
    { 
        //alert(i + " " + j);
        if (i=j)
        {
            arr[i][j]=0;
        }
        else
        {
            arr[i][j]=1;
        }
    }
}

i=j is assigning the value of j to i. If you want to compare, then you need to do i === j — thefourtheye
– thefourtheye, Commented Apr 28, 2015 at 2:44
Mind if I ask, what's the point of using address.length instead of just 4? — dmeglio
– dmeglio, Commented Apr 28, 2015 at 2:48
dman, this is just a test, eventually I will have more than 25. It is still not working: jsfiddle.net/anna5xp6/1 — Tim Zheng
– Tim Zheng, Commented Apr 28, 2015 at 2:50

Arun P Johny · Accepted Answer · 2015-04-28 02:47:32Z

3

You have 2 problems in your script

for (i = 0; i < address.length; i++) {
    //need to initialize arr[i] else `arr[i]` will return undefined
    arr[i]= [];
    for (j = 0; j < address.length; j++) {
        //need == not =
        if (i == j) {
            arr[i][j] = 0;
        } else {
            arr[i][j] = 1;
        }
    }
}

console.log(arr)

Where the if..else can be replaced by a ternary operator

for (j = 0; j < address.length; j++) {
    arr[i][j] = i == j ? 0 : 1;
}

Demo: Fiddle

answered Apr 28, 2015 at 2:47

Arun P Johny

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