JavaScript indexOf function not producing the desired results

I am currently experimenting to determine whether a specific value already exists in an array.

In this scenario, the value of "node1" remains constant. The two arrays are exactly the same.

Yet, the same node is appended to the array twice despite the indexOf(node1) evaluation. http://jsfiddle.net/v9yxj5hm/2/

var tree_rows = []; 

var node1 = ['Workplace','Revenue Overall',0];  
if (tree_rows.indexOf(node1) == -1){ tree_rows.push(node1); } 

node1 = ['Workplace','Revenue Overall',0]; 
if (tree_rows.indexOf(node1) == -1){ tree_rows.push(node1); } 

alert(tree_rows)
javascript

Answer №1

The comparison performed by the .indexOf() method is similar to that of the === strict equality operator. Two separate arrays will never be considered equal under these conditions.

When creating objects using array or object literal expressions, each object created is unique. Simply because two literal expressions appear identical does not imply they are the same object.

Answer №2

Another way to declare variables

let node1 = ['Workplace','Revenue Overall',0];

By reusing the variable node1 when it already exists, a new entry in the lexical environment is created. This can cause the indexOf method to not find the previous value for that entry. Consequently, node1 ends up being added to the array a second time.

Answer №3

Check to see if each element in node1 exists in tree_rows. Is this what you're looking for?

var tree_rows = []; 

var node1 = ['Workplace','Revenue Overall',0];  
for (i in node1) { if (tree_rows.indexOf(node1[i]) == -1){ tree_rows.push(node1[i]); }} 

node1 = ['Workplace','Revenue Overall',0]; 
for (i in node1) { if (tree_rows.indexOf(node1[i]) == -1){ tree_rows.push(node1[i]); }}

alert(tree_rows)

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