If you are at the origin of the file, it’s simpler to redact it as a JSON standard :
let s =
[ [[-7.5,-7.5,-5.0], [-2.5,-7.5,0.0], [2.5,-7.5,0.0], [7.5,-7.5,-5.0]], [[-7.5,-2.5,-7.5], [-2.5,-2.5,5.0], [2.5,-2.5,5.0], [7.5,-2.5,-7.5]], [[-7.5, 2.5, 0.0], [-2.5,2.5,-5.0], [2.5,2.5,-5.0], [7.5, 2.5, 0.0]], [[-7.5, 7.5,-5.0], [-2.5,7.5,-10.00], [2.5,7.5,-10.00], [7.5,7.5,-5.0]] ]
( just add a surrounding pair of brackets)
You just have to read it with parse, and that’s all.
let big = JSON.parse(s)
// access
console.log(big). // array(4) most external
console.log(big[0]) // array(4) a line
console.log(big[0][0]) // array(3) one vector
console.log(big[0][0][0]) // an element -7.5.
HTH