Find the length of an Array consisting of 2D arrays

Question

Is there a way to find the length of this array, and all the sub arrays inside it. Meaning 13 and not 6? Without having to use loops and adding up all the elements inside the arrays.

I'm looking for one command that can do this.

[1, [4, 5, 2, 1], 2, [4, 5, 2, 6], 2, [3, 3]]

Answer 1

尝试扁平化

[].concat.apply([], [1, [4, 5, 2, 1], 2, [4, 5, 2, 6], 2, [3, 3]]).length

Answer 2

A bit of a hack, but you can do

arr.toString().split(',').length

join(',') would work as well, it flattens everything

 var arr = [1, [4, 5, 2, 1], 2, [4, 5, 2, 6], 2, [3, 3]]; console.log(arr.toString().split(',').length) 

if all you wanted was the number of indices in total

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If the array contains commas inside the indices, those could be removed for the same effect

JSON.stringify(arr).replace(/"(.*?)"/g,'1').split(',').length

Answer 3

• Array#reduce could be used but [at your own risk]

• Use Array.isArray to determine whether the passed value is an Array .

 var input = [1, [4, 5, 2, 1], 2, [4, 5, 2, 6], 2, [3, 3]]; var length = input.reduce(function(a, b) { return a + (Array.isArray(b) ? b.length : 1); }, 0); console.log(length);