Show all function: Try Array.prototype & Array in browser console.
foreach
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| let numbers = [1, 2, 3, 4, 5];
// each element in a func
numbers.forEach((element, index, arr) => {
console.log(`a[${index}] = ${element}`);
});
// a[0] = 1
// a[1] = 2
// a[2] = 3
// a[3] = 4
// a[4] = 5
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map
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| let numbers = [1, 2, 3, 4, 5];
// [] => [] (some size)
let numbers2 = numbers.map((e, index, arr) => {
return e * index;
});
console.log(numbers2); // [0, 2, 6, 12, 20]
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filter
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| let numbers = [1, 2, 3, 4, 5];
// [] => fuc => [] (some left)
let numbers3 = numbers.filter((e, index, arr) => {
return arr.indexOf(e) === index;
}); // remove duplication
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reduce
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| let numbers = [1, 2, 3, 4, 5];
// [] => 1
let numbers4 = numbers.reduce((prev, cur, curIndex, arr) => {
return prev + cur;
}, 0);
console.log(numbers4); // 15
let maxValue = numbers.reduce((prev, cur) => {
if (prev > cur) return prev;
else return cur;
}, -Infinity);
console.log(maxValue); // 5
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slice
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| let numbers = [1, 2, 3, 4, 5];
// [start, end)
// [start to end)
let first2 = numbers.slice(0, 2);
let shallowCopy = numbers.slice(); // could shallow copy an array
shallowCopy[5] = 100;
let last3 = numbers.slice(-3);
let startFrom1 = numbers.slice(1);
console.log([first2, shallowCopy, last3, startFrom1]);
// [ [ 1, 2 ], [ 1, 2, 3, 4, 5, 100 ], [ 3, 4, 5 ], [ 2, 3, 4, 5 ] ]
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splice
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| let numbers = [1, 2, 3, 4, 5];
let deleted = numbers.splice(1, 2, 'add', 'add'); // (start point, num, ...add-in)
console.log(numbers, deleted);
//[ 1, 'add', 'add', 4, 5 ] [ 2, 3 ]
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sort
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| let numbers = [75, 22, 18, 10, 100, 214, 1];
numbers.sort(); // not sort by number
// If compareFn not provided, sort everything base on string.
console.log(numbers); // [1, 10, 100, 18, 214, 22, 75]
// CompareFn return a Number. If return < 0, a goes first. If return > 0, b goes first. If return 0, not change
numbers.sort((a, b) => {
return a - b; // if use a > b, function only return 0 and 1.
});
console.log(numbers); // [ 1, 10, 18, 22, 75, 100, 214]
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concat
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| let a = [1, 2, 3];
let b = [10, 20, 30];
let c = a.concat(b);
let d = a.concat(c, 100, a);
console.log(c); // [ 1, 2, 3, 10, 20, 30 ]
console.log(d); // [ 1, 2, 3, 1, 2, 3, 10, 20, 30, 100, 1, 2, 3]
shallowCopy = d.concat(); // also a shallow copy
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fill
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| let numbers = [1, 2, 3, 4, 5];
// fill
let out = numbers.fill(0, 2, 4); // (value, start, end)
console.log(out); // [ 1, 2, 0, 0, 5 ]
console.log(numbers); // [ 1, 2, 0, 0, 5 ]
let fillInNumber = (n) => {
return Array(n)
.fill(0)
.map((_, idx) => idx);
};
console.log(fillInNumber(10)); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
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include
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| let names = ['andy', 'bob', 'eve'];
console.log(names.includes('bob')); // true
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join
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| let names = ['andy', 'bob', 'eve'];
let res = names.join();
console.log(res); // andy,bob,eve
res = names.join(' - ');
console.log(res); // andy - bob - eve
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reverse
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| let names = ['andy', 'bob', 'eve'];
let str = 'coding is fun';
res = str.split(' ').reverse().join(' ');
console.log(res); // fun is coding
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push
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| let numbers = [0];
let len = numbers.push(1, 2, 3, 4, 5);
console.log(len); // 6
console.log(numbers); // [ 0, 1, 2, 3, 4, 5 ]
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pop
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| let numbers = [1, 2, 3, 4, 5];
let lastItem = numbers.pop();
console.log(lastItem); // 5
console.log(numbers); // [1,2,3,4]
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unshift
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| let numbers = [1, 2, 3, 4, 5];
len = numbers.unshift(-1, -2); // push at begin
console.log(len); // 7
console.log(numbers); // [-1, -2, 1, 2, 3, 4, 5]
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shift
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| let numbers = [1, 2, 3, 4, 5];
let res = numbers.shift();
console.log(res, numbers); // 1 [2, 3, 4, 5]
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indexOf & lastIndexOf
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| let names = ['florin', 'ivan', 'liam', 'ivan', 'liam'];
let idx = names.indexOf('jay');
console.log(idx); // -1
idx = names.indexOf('liam'); // return first index
console.log(idx); // 2
idx = names.lastIndexOf('liam');
console.log(idx); // 4
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every
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| let numbers = [1, 2, 3, 4, 5];
// each => bool
let res = numbers.every((each) => {
return each > 0;
});
console.log(res); // true
const people = [{ name: '1' }, { name: '1' }, { name: '1' }, { surname: '1' }];
res = people.every((each) => each.name !== undefined);
console.log(res); // false
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some
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| let numbers = [1, 2, 3, 4, 5];
let res = numbers.some((each) => {
return each > 4;
});
console.log(res); // true
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find
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| let people = [
{
name: 'florin',
age: 25,
},
{
name: 'ivan',
age: 20,
},
{
name: 'lima',
age: 18,
},
];
let res = people.find((each) => {
return each.name == 'ivan';
}).age;
console.log(res); // 20
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findIndex
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| const numbers = [1, 2, 3, 4, 5];
let res = numbers.findIndex((each) => {
return each === 4;
});
console.log(res); // 3
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flat
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| let array = [1, [2, [3, [4, [5]]]]];
console.log(array.flat()); // [1, 2, [3, [4, [5]]]]
console.log(array.flat(3)); // [1, 2, 3, 4, [5]]
console.log(array.flat(Infinity)); // [1, 2, 3, 4, 5]
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flatMap
keys & values & entries
These 3 methods returns a new Array Iterator object
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| let numbers = [10, 20, 30, 40, 50];
let iterator_keys = numbers.keys();
console.log(iterator_keys.next().value); // 0
for (let i of iterator_keys) {
console.log(i); // 1 2 3 4
}
let iterator_values = numbers.values();
console.log(iterator_values.next().value); // 10
for (let i of iterator_values) {
console.log(i); // 20 30 40 50
}
let iterator = numbers.entries();
console.log(iterator.next().value); // [0,10]
for (let i of iterator) {
console.log(i); // [1,20] [2,30] [3,40] [4,50]
}
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copyWithin
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| const array1 = ['a', 'b', 'c', 'd', 'e'];
// copy to index 0 the element at index 3
console.log(array1.copyWithin(0, 3, 4));
// expected output: Array ["d", "b", "c", "d", "e"]
// copy to index 1 all elements from index 3 to the end
console.log(array1.copyWithin(1, 3));
// expected output: Array ["d", "d", "e", "d", "e"]
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toLocaleString & toString
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| const array1 = [1, 2, 'a', '1a'];
console.log(array1.toString());
// expected output: "1,2,a,1a"
const array1 = [1, 'a', new Date('21 Dec 1997 14:12:00 UTC')];
const localeString = array1.toLocaleString('en', { timeZone: 'UTC' });
console.log(localeString);
// expected output: "1,a,12/21/1997, 2:12:00 PM",
// This assumes "en" locale and UTC timezone - your results may vary
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from
Make a shallow copy from a iterable object
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| const str = '1234567';
const res = Array.from(str, (each, index) => Number(each));
console.log(res);
let numbers = [1, 2, 3, 4, 3, 2, 1, 3, 3, 4, 3, 5, 2];
let s = new Set(numbers);
numbers = Array.from(s);
console.log(numbers);
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of
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| Array.of(7); // [7]
Array.of(1, 2, 3); // [1, 2, 3]
Array(7); // [ , , , , , , ]
Array(1, 2, 3); // [1, 2, 3]
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isArray
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| let numbers = [1, 2, 3, 4, 3, 2, 1, 3, 3, 4, 3, 5, 2];
const str = '1234567';
let number = 12;
console.log(Array.isArray(numbers)); // true
console.log(Array.isArray(str)); // false
console.log(Array.isArray(number)); // false
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