Methods and properties
get | |
prototype[@@unscopables] | |
prototype.length | |
prototype[@@iterator]() | |
prototype.at() | |
prototype.concat() | |
prototype.copyWithin() | |
prototype.entries() | |
prototype.every() | Returns true if a function returns true for each element in the array. Compare with some() |
prototype.fill() | |
prototype.filter() | |
prototype.find() | |
prototype.findIndex() | |
prototype.findLast() | |
prototype.findLastIndex() | |
prototype.flat() | |
prototype.flatMap() | |
prototype.forEach() | Iterate over the elements of the array. Compare also with the forEach() method of NodeList and the for (e of a) and for (k in x) Javascript language construct. |
from() | |
prototype.group() | Experimental |
prototype.groupToMap() | Experimental |
prototype.includes() | |
prototype.indexOf() | |
isArray() | |
prototype.join() | |
prototype.keys() | |
prototype.lastIndexOf() | |
prototype.map() | |
of() | |
prototype.pop() | |
prototype.push() | |
prototype.reduce() | |
prototype.reduceRight() | |
prototype.reverse() | |
prototype.shift() | |
prototype.slice() | Compare with the slice() method of the String object. |
prototype.some() | Compare with every() |
prototype.sort() | |
prototype.splice() | |
prototype.toLocaleString() | |
prototype.toString() | |
prototype.unshift() | |
prototype.values() | |
forEach
It's possible to modify the objects in the function that is called by forEach().
In the following example, the objects are added the new property txt:
let o1 = {num: 5};
let o2 = {num: 3};
let o3 = {num: 7};
[o1, o2, o3].forEach(o => o.txt = '*'.repeat(o.num));
print(o1.txt);
print(o2.txt);
print(o3.txt);
sort
js> let a = [
{ nam: 'abc', id: 5 },
{ nam: 'def', id: 2 },
{ nam: 'ghi', id: 9 },
{ nam: 'jkl', id: 3 },
{ nam: 'mno', id: 3 }
];
js> s = a.sort( (p, q) => p.id > q.id );
js> s.forEach( e => print(e.nam) );
reduce
js> let reduced = [4,2,1,9].reduce( (a, e) => { print(`a = ${a}, e = ${e}`); return a+e;} );
a = 4, e = 2
a = 6, e = 1
a = 7, e = 9
js> print(reduced);
16
Use an init value for accumulator a (here: 3):
js> let reduced = [4,2,1,9].reduce( (a, e) => { print(`a = ${a}, e = ${e}`); return a+e;}, 3 );
a = 3, e = 4
a = 7, e = 2
a = 9, e = 1
a = 10, e = 9
slice
js> let a = ['zero', 'one', 'two', 'three', 'four', 'five'];
js> a.slice()
["zero", "one", "two", "three", "four", "five"]
js> a.slice(1)
["one", "two", "three", "four", "five"]
js> a.slice(2)
["two", "three", "four", "five"]
js> a.slice(2,3)
["two"]
js> a.slice(2,4)
["two", "three"]
every
every(f) returns true if the function f returns true for all elements in the array:
js> a = [ 7, 5, 3, 9, 8 ];
js> a.every( e => e > 0 );
true
js> a.every( e => e > 5 );
false
concat
js> let a = ['zero', 'one', 'two', 'three', 'four', 'five'];
js> a.concat('six', 'seven')
["zero", "one", "two", "three", "four", "five", "six", "seven"]
js> [].concat(7, 3, 9);
[7, 3, 9]
js> [1,2].concat( [3, 4], [5, 6]);
[1, 2, 3, 4, 5, 6]
js> [1,2].concat( [[3, 4], [5, 6]], [7], [[8]]);
[1, 2, [3, 4], [5, 6], 7, [8]]
push
push adds an element to the end of an array and returns the number of elements in the array after adding the elements.
js> let a = [1, 2, 3];
js> a.push(4,5)
5
js> a
[1, 2, 3, 4, 5]
toString
<!DOCTYPE HTML>
<html>
<head>
<title>Javasctipt Array.toString()</title>
<meta content="text/html;charset=utf-8" http-equiv="Content-Type">
<script type="text/javascript">
function init() {
var out = document.getElementById('out');
var arr = new Array(1, 42, 2014);
out.innerHTML = arr.toString(); // 1,42,2014
}
</script>
</head>
<body onload="init();">
<div id="out"></div>
</body>
</html>
flat
js> let a =
[
[1,2],
[
3,
[4,5,
[
6,7
],
8
]
]
];
js> a.flat()
[1, 2, 3, [4, 5, [6, 7], 8]]
js> a.flat().flat()
[1, 2, 3, 4, 5, [6, 7], 8]
js> a.flat().flat().flat()
[1, 2, 3, 4, 5, 6, 7, 8]
x.flat(n) is equivalent to applying flat() n times to x:
js> a.flat(2)
[1, 2, 3, 4, 5, [6, 7], 8]
It's possible to use Infinity for n:
js> a.flat(Infinity)
[1, 2, 3, 4, 5, 6, 7, 8]