Javascript Array Methods

Front 1

join()

Back 1

The string conversions of all array elements are joined into one string. Accepts seperators.

string = array.join(separator)

Hint 1

var a = [1, 2, 3];

var b = a.join();
// returns "1,2,3"

var b = a.join(' + ');
// returns "1 + 2 + 3"

Front 2

length()

Back 2

Returns the number of values in the array. Allows for truncating and extending. Starts at 0 index.

array.length

Hint 2

var a = [1, 2, 3, 4, 5];

a.length
// returns 4

Front 3

pop()

Back 3

Removes the last element from an array and returns that value to the caller.

array.pop()

Hint 3

var a = [1, 2, 3, 4];

var pop = a.pop();
// returns 4
// a becomes [1, 2, 3]

Front 4

push()

Back 4

Appends values to an array. Accepts unlimited parameters.

array.push(element1, ..., elementN)

Hint 4

var a = [1, 2];

a.push(3, 4);
// a becomes [1,2,3,4]

Front 5

reverse()

Back 5

The reverse method reverse the elements of an array, mutating the array, and returning a reference.

array.reverse()

Hint 5

var a = [1, 2, 3];

a.reverse();
// returns [3, 2, 1]

Front 6

shift()

Back 6

Removes the (first) element at the zeroeth index and shifts the values at consecutive indexes down, then returns the removed value.

array.shift()

Hint 6

var a = [1, 2, 3, 4, 5]

a.shift();
// returns 1
// a becomes [2,3,4,5]

Front 7

unshift()

Back 7

Inserts the given values to the beginning of an array. Returns the new length of the array. Accepts unlimited parameters.

array.unshift(element1, ..., elementN)

Hint 7

var a = [1, 2, 3];

a.unshift(0);
// returns 4
// a becomes [0, 1, 2, 3]

Front 8

slice()

Back 8

Does not alter the original array, but returns an array of elements sliced from the original array leaving the original alone.

array.slice(begin, end)

Hint 8

var a = [1, 2, 3, 4, 5];

var b = a.slice(1, 3);
// returns [2, 3]

Front 9

splice()

Back 9

Removes elements and inserts elements in it's place. If a different amount, the array will have a different length. Returns removed elements.

array.splice(index , howMany[, element1[, ...[, elementN]]])

Hint 9

var a = [1, 2, 3, 4, 5];

var b = a.splice(1, 2, 'a', 'b', 'c')
// b is assigned [2, 3]
// a becomes [1, 'a', 'b', 'c', 4, 5]

Front 10

concat()

Back 10

Creates a new array consisting of the elements in the this object on which it is called. followed (in order) by the elements of that argument.

array.concat(value1, value2, ..., valueN)

Hint 10

var a = [1, 2, 3];
var b = ['a', 'b', 'c'];

var ab = a.concat(b);
// creates array [1, 2, 3, 'a', 'b', 'c'];

Front 11

indexOf()

Back 11

Compares an element to elements of the array using strict equality. if greater than the array's length it will return -1;

array.indexOf(searchElement[, fromIndex])

Hint 11

var a = [1, 2, 3];

var b = a.indexOf(0);
// b is assigned 1

var b = a.indexOf(7);
// b is assigned -1

Front 12

sort()

Back 12

Sorts in lexicographic (1, 2, 3) order unless function is supplied, the array elements are sorted according to the return value of the compare function. If a and b are two elements being compared, then:

array.sort([compareFunction])

Hint 12

var a = [1, 3, 2, 4, 5];

function compare(a, b) {
return b - a;
}

a.sort()
// returns [1,2,3,4,5]

a.sort(compare)
// return [5,4,3,2,1]

Front 13

map()

Back 13

Provides a callback function once for each element in an array, in order, and constructs a new array from the results. Only works on indexes of the array which have assigned values; it is not invoked for indexes which have been deleted or which have never been assigned values.

array.map(callback[, thisArg])

Hint 13

var a = [1, 3, 2, 4];

var b = a.map(function (x) {
return x.toString()
});
// b is assigned ['1', '2', '3', '4']

Front 14

lastIndexOf()

Back 14

lastIndexOf compares searchElement to elements of the Array using strict equality.

Search array from the end. Defaults to the array's length. If the index is greater than or equal to the length of the array, the whole array will be searched. If negative, it is taken as the offset from the end of the array.

array.lastIndexOf(searchElement[, fromIndex])

Hint 14

var a = [1, 3, 2, 4, 2];

var b = a.lastIndexOf(2);
// b is 4

b = a.lastIndexOf(2, 3);
//b is 2

Front 15

toString()

Back 15

Joins the array and returns one string containing each array element separated by commas.

array.toString()

Hint 15

var a = [1, 2, 3, 4];

var b = a.toString();
// b is assigned "1,2,3,4"

Front 16

filter()

Back 16

filter calls a provided callback function once for each element in an array, and constructs a new array of all the values for which callback returns a true value. callback is invoked with three arguments: (value, index, array)

array.filter(callback[, thisObject])

Hint 16

var a = [1, 2, 3, 4, 5, 6];

a.filter(function(value, index) {
return value > 3;
});
//returns [4, 5, 6]

Front 17

every()

Back 17

array.every(callback[, thisObject])

Front 18

some()

Back 18

array.some(callback[, thisObject])