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Discussion on: What is the oddest JavaScript behavior?

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Pankaj Doharey • Edited on

const a = Array(3).fill([null,null,null] )

// Is not the same as 

const b =  [[null,null, null],[null,null, null],[null,null, null]]

/* because if you try to fill an element in one array in the first example 
it fills all the array with the same element */

a[1][2] = "X";

//This results in the following.

/* 
=> 

[[null, null, "X"]
 [null, null, "X"]
 [null, null, "X"]] /*


/* Aah freaking javascript. */