{
const array = [];
for (let i = 0; i < 10; i++) {
array.push(i);
}
return array;
}
d3.range(10)
{
const array = [5, 3, 1, 0, null, 3];
const newArray = [];
for (let i = 0; i < array.length; i++) {
if (array[i] !== null) {
newArray.push(array[i]);
}
}
return newArray;
}
[5, 3, 1, 0, null, 3].filter((n) => n !== null)
{
const array = [];
for (let i = 0; i < 10; i++) {
array.push(i);
}
const newArray = [];
for (let i = 0; i < array.length; i++) {
newArray.push(array[i] * 3);
}
return newArray;
}
d3.range(10).map((n) => n * 3)
{
const array = [];
for (let i = 0; i < 10; i++) {
array.push([]);
for (let j = 0; j < 10; j++) {
array[i].push(j);
}
}
return array;
}
d3.range(10).map((n) => d3.range(10))
[2, 5, 8, 12].reduce((acc, val) => acc * val, 1)
[2, 5, 8, 12].reduce((acc, val) => acc + val, 0)
[
{ order: "carnivora", animal: "cat" },
{ order: "carnivora", species: "dog" },
{ order: "carnivora", species: "ferret" },
{ order: "passeriformes", species: "canary" },
{ order: "columbiformes", species: "pigeon" },
{ order: "artiodactyl", species: "pig" },
{ order: "artiodactyl", species: "sheep" }
].reduce((acc, animal) => {
//check if the accumulator already has a key for the animal's order
if (acc[animal.order]) {
//if so, add the animal
acc[animal.order].push(animal);
} else {
//otherwise, make a new key and add the current animal to it in an array
acc[animal.order] = [animal];
}
return acc;
}, {}) //the {} means we are starting with an empty object
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