Mike M Mike M - 2 years ago 135
Javascript Question

Concat in an empty array in Javascript

I was browsing through some code and I was wondering how this could be useful


In my understanding it is the same as


Why the 'concat' fuss?

Answer Source

You want to use .concat when you need to flatten the array and not have an array consisting of other arrays. E.g.

var a = [1,2,3];
var b = [4];

Scenario 1

// Result: [4, [1,2,3]]

Scenario 2

// Result: [4,1,2,3]

So both of your scenarios in an array of array. Since [].concat() results in an array only, pushing both [row], [].concat(row) results in same result.

But if you want a flattened array, there is a slight change needed in your code, that you have to .concat the array row with grid and not .push the result of concat to it, as shown in scenario 2

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