How to find the max/min of a nested array in javascript?
If you have a nested array of numbers (arrays = [[1, 2], [20, 3]]
), nest d3.max:
var max = d3.max(arrays, function(array) {
return d3.max(array);
});
Or equivalently, use array.map:
var max = d3.max(arrays.map(function(array) {
return d3.max(array);
}));
If you want to ignore string values, you can use array.filter to ignore strings:
var max = d3.max(arrays, function(array) {
return d3.max(array.filter(function(value) {
return typeof value === "number";
}));
});
Alternatively, if you know the string is always in the first position, you could use array.slice which is a bit more efficient:
var max = d3.max(arrays, function(array) {
return d3.max(array.slice(1));
});
Yet another option is to use an accessor function which returns NaN
for values that are not numbers. This will cause d3.max to ignore those values. Conveniently, JavaScript's built-in Number
function does exactly this, so you can say:
var max = d3.max(arrays, function(array) {
return d3.max(array, Number);
});
Use this:
function arrmax(arrs) {
var toplevel = [];
var f = function(v) {
return !isNaN(v);
};
for (var i = 0, l = arrs.length; i<l; i++) {
toplevel.push(Math.max.apply(window, arrs[i].filter(f)));
}
return Math.max.apply(window, toplevel);
}
or better:
function arrmax(arrs) {
if (!arrs || !arrs.length) return undefined;
var max = Math.max.apply(window, arrs[0]), m,
f = function(v){ return !isNaN(v); };
for (var i = 1, l = arrs.length; i<l; i++) {
if ((m = Math.max.apply(window, arrs[i].filter(f)))>max) max=m;
}
return max;
}
See MDN for Array.filter method details.