An array is a linear data structure that represents a collection of elements. In JavaScript, arrays don't have a fixed size, while their contents can be of any valid type, even arrays themselves. Arrays are probably the most commonly used data structure and come with a plethora of methods that allow easy manipulation and transformation of their contents.
const nums = [1, 2, 3];
const strs = Array.from('est');
nums.push(6);
nums.push(4, 9);
strs.unshift('t');
nums.length; // 6
nums[nums.length - 1]; // 9
strs[0]; // 't'
strs[2]; // 's'
nums.slice(1, 3); // [2, 3]
nums.map(n => n * 2); // [2, 4, 6, 12, 8, 18]
nums.filter(n => n % 2 === 0); // [2, 6, 4]
nums.reduce((a, n) => a + n, 0); // 25
strs.reverse(); // ['t', 's', 'e', 't']
strs.join(''); // 'test'
A set is a linear data structure that represents an ordered collection of unique values. Sets in JavaScript can store any valid type of value, however each value can only occur once based on value equality checking.
const nums = new Set([1, 2, 3]);
nums.add(4);
nums.add(1);
nums.add(5);
nums.add(4);
nums.size; // 5
nums.has(4); // true
nums.delete(4);
nums.has(4); // false
[...nums]; // [1, 2, 3, 5]
nums.clear();
nums.size; // 0
A map is an associative data structure that represents a keyed collection of elements. Each key in a JavaScript Map has to be unique and either a primitive value or an object, whereas the values of the map can be of any valid type.
const items = new Map([
[1, { name: 'John' }],
[2, { name: 'Mary' }]
]);
items.set(4, { name: 'Alan' });
items.set(2, { name: 'Jeff' });
items.size; // 3
items.has(4); // true
items.get(2); // { name: 'Jeff' }
items.delete(2);
items.size; // 2
[...items.keys()]; // [1, 4]
[...items.values()]; // [{ name: 'John' }, { name: 'Alan' }]
items.clear();
items.size; // 0
Snippet collection
A guide to some of the most commonly-used data structures, along with JavaScript implementations and examples.
Learn the basics of the destructuring assignment syntax in JavaScript ES6 and improve your code with this easy guide.
JavaScript, Object
Deeply merges two objects, using a function to handle keys present in both.
JavaScript, Object
Maps the keys of an object using the provided function, generating a new object.