JSFiddle - React, Tailwind, and code Playground

JavaScript

var arr = [[1,  37.8, 80.8, 41.8],
    [2,  30.9, 69.5, 32.4],
    [3,  25.4,   57, 25.7],
    [4,  11.7, 18.8, 10.5],
    [5,  11.9, 17.6, 10.4],
    [6,   8.8, 13.6,  7.7],
    [7,   7.6, 12.3,  9.6],
    [8,  12.3, 29.2, 10.6],
    [9,  16.9, 42.9, 14.8],
    [10, 12.8, 30.9, 11.6],
    [11,  5.3,  7.9,  4.7],
    [12,  6.6,  8.4,  5.2],
    [13,  4.8,  6.3,  3.6],
    [14,  4.2,  6.2,  3.4]];

var flattened = [], minValue, maxValue;
arr.forEach(function (v) {
    Array.prototype.push.apply(flattened, v);
});

minValue = Math.min.apply(null, flattened);
maxValue = Math.max.apply(null, flattened);

console.log('min: ' + minValue, ' max: ' + maxValue);