USEFUL JAVASCRIPT ARRAY AND OBJECT METHODS
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- FILTER: creates a new array based on whether the items of an array pass a certain condition.
const studentsAge = [17, 16, 18, 19, 21, 17];
const ableToDrink = studentsAge.filter(age => age>18 );
//ableToDrink = [19,21]
2. MAP: creates a new array by manipulating the value in another array. It is great for data manipulation, it is immutable method.
const numbers = [2,3,4,5];
const dollars = numbers.map( number => ‘$’ + number);
//dollars [ ‘$2’, ‘$3’, ‘$4’, ‘$5’]
3.REDUCE: This method uses an accumulator to reduce all items in an array to a single value. great for calculating totals. The returned value can be of any type(i.e.object, array, string, integer).
const numbers = [5,10,15];
const total = numbers.reduce(accumulator, currentValue) => accumulator +currentValue);
//output total = 30;
4.FOREACH: Applies a function on each item in an array. The foreach method executes provided function once for each element.
const emotions = [‘happy’, ‘sad’, ‘angry’]
emotions.forEach( emotion => console.log(emotion));
//output
‘happy’ ‘sad’ ‘angry’
5.SOME: The some() method tests whether at least one element in the array passes the test implemented by the provided function. It returns a Boolean value.
const user = [‘user’, ‘user’, ‘user’, ‘admin’]
const containsAdmin = user.some(element => element ===’admin’)
//output: containsAdmin will be equal to true
6.EVERY: The every() method tests whether all element in the array pass the test implemented by the provided function. It returns a Boolean value.
const ratings = [3,4,5,3,5];
const goodRating = ratings.every(rating => rating>=3 );
//output: goodRating will be true
7.INCLUDES: The includes() method determines whether an array includes certain value among its entries, returns Boolean.
const names = [‘Sophie’, ‘George’, ‘waldo’];
const includesWaldo = names. Includes(‘waldo’);
//output : True
