Kelvin WangonyaThis'll be a quick one.
Say you want to check if a specific element exists in an array. There's a couple of ways to do that:
ES5
indexOf()
indexOf returns the index of the first matching item found, or -1 if not found.
// check if a Fortnite ninja exists in the array
const ninjas = ['Alchemist', 'Brawler', 'Skirmisher', 'Harvester']
console.log(ninjas.indexOf('Brawler')) // 1
console.log(ninjas.indexOf('Harvester')) // 3
console.log(ninjas.indexOf('Assassin')) // -1 (doesn't exist)
lastIndexOf()
lastIndexOf() returns the index of the last matching item found, or -1 if not found.
// check if a Fortnite ninja exists in the array
// note that 'Brawler' exists twice
const ninjas = ['Alchemist', 'Brawler', 'Skirmisher', 'Harvester', 'Brawler', 'Stonefoot']
console.log(ninjas.lastIndexOf('Brawler')) // 4 (last one returned)
console.log(ninjas.lastIndexOf('Harvester')) // 3
console.log(ninjas.lastIndexOf('Assassin')) // -1 (doesn't exist)
ES6
find()
The find() method returns the value of the first element in the array that satisfies the provided testing function. Otherwise undefined is returned.
const ninjas = [
{name: 'Alchemist'},
{name: 'Brawler'},
{name: 'Skirmisher'},
{name: 'Harvester'}
]
console.log(ninjas.find(ninja => ninja.name === 'Harvester')); // {name: "Harvester"}
console.log(ninjas.find(ninja => ninja.name === 'Assassin')); // undefined
findIndex()
Returns the index of the first element in the array that satisfies the provided testing function. Otherwise -1 is returned.
const ninjas = [
{name: 'Alchemist'},
{name: 'Brawler'},
{name: 'Skirmisher'},
{name: 'Harvester'}
]
console.log(ninjas.findIndex(ninja => ninja.name === 'Harvester')); // 3
console.log(ninjas.findIndex(ninja => ninja.name === 'Assassin')); // -1
ES7
includes()
The includes() method determines whether an array includes a certain element, returning true or false as appropriate. For example, a.includes(value) returns true if a contains value
const ninjas = ['Alchemist', 'Brawler', 'Skirmisher', 'Harvester']
console.log(ninjas.includes('Brawler')); // true
console.log(ninjas.includes('Assassin')); // false
a.includes(value, i) returns true if a contains value after (or at) the position i
const ninjas = ['Alchemist', 'Brawler', 'Skirmisher', 'Harvester']
console.log(ninjas.includes('Skirmisher', 1)); // true
console.log(ninjas.includes('Skirmisher', 2)); // true
console.log(ninjas.includes('Skirmisher', 3)); // false
Let me know of any other interesting ways I may have missed :)
