array splice and console.log [duplicate]

Question

When I perform operations on an array in javascript, console.log shows the array as having been already changed BEFORE I do an operation on the array. I can reproduce this in chrome and firefox. Anyone know why this is?

var myTabs = [[0,0,0],
              [0,0,0],
              [0,0,0],
              [0,0,0]];
console.log(myTabs);
myTabs[0].splice(1, 1);
console.log(myTabs);

See this for code:

https://jsfiddle.net/mxrh33t0/1/

Answer 1

When you expand a logged object in Chrome, you are expanding the last reference to it, not a copy of that object at the moment that it was logged.

In your case, the last reference was to the array after the splice() method had been called. If you would like to verify the difference, you will have to be more specific with your logging:

var myTabs = [[0,0,0],
              [0,0,0],
              [0,0,0],
              [0,0,0]];
console.log(myTabs[0].join(","));
myTabs[0].splice(1, 1);
console.log(myTabs[0].join(","));

You can expand on that if you really want to see more.